Rules
The board is a grid. Some cells hold a number. Shade empty cells black for the sea, or mark a dot on a cell that stays white. The puzzle is finished when every empty cell is sea or a dot and the rules hold.
- One sea. The black cells are one piece, joined across or down, never diagonally.
- No pool. No 2×2 block is all sea.
- Islands match their numbers. Every white region has exactly one number, and that many cells, counting the number.
- A corner touch is allowed. Two islands never share a side. They may touch at a corner.
- A number stays white. The Sea tool does not shade a number.
A finished 3×3. The two 1s share a corner and no side. The sea is drawn teal, the way a solved board looks. No dots: every white cell here is a number.
- Sea
- Dot
- Number
A dot is a white cell you have marked. An unknown cell is neither sea nor a dot. Islands never share an edge. They may touch at a corner, as these two 1s do. Every Nurikabe on PuzzleKite has one solution, and you can finish it by logic. The windows in this guide are for the sentences. They are not sizes the play page deals.
First moves
Shade around a finished 1, wall off a full island, put sea between two islands, and dot the cells the sea rules force.
A finished 1 Easy
A 1 is already a finished island. Shade every cell that shares a side with it. Start here. Later sections grow an island past its number. This one does not grow.
On a blank board the first sea is the cell under the corner 1. The ring is amber, and the new sea stays black. A 1 in the middle has four neighbours. A 1 in the corner has two. All of them are sea.
The same sentence writes the other three seas, in this order, before any other idea:
- Shade the cell to the right of the corner 1.
- Shade the cell under the centre 1.
- Shade the cell to the right of the centre 1.
After those four seas, the three cells that are left cannot be reached by either 1. They are sea too, and the grid matches the finished picture in the rules. That reach is nothing can reach it.
Wall off a full island Easy
Once the white cells of an island, counting the number, equal the number, shade every open neighbour. That wall is sea. Do this as soon as the island is big enough. Leaving a side open joins the island to whatever is next door.
The dot under the 2 finishes the island. It has two cells. The cell to the right of the 2 shares a side with the number, so it is sea. Hint says the island is already full.
From a blank board this puzzle walls the 1 first, then reaches cells, then places a pool dot, and only then writes this sea. The picture keeps the dot alone.
The neighbour that only touches a dotted cell is the same rule. Hint uses a second sentence for it: the cell touches an island that is already full. The second sentence is an easy one. The small board that shows it cleanly is a medium grid, because that grid later needs the count in section 3.
The 2’s island is the number and the dot under it. The cell to the left of the dot shares a side with the dot and not with the 2, so it is sea. The cell between the 3 and the 2 is already sea.
Between two islands Easy
A cell that shares a side with two different islands is sea. If it stayed white, the two islands would become one region with two numbers. Look for this wherever two numbers face each other across one cell, and wherever a dot on one island meets another island. Some easy grids never have the pair. Use it when you see it.
The first mark is the sea between the two 2s. Each finished island is the 2 and the cell under it. A column of sea sits between them, so they do not touch at a corner. The corner touch stays on the rules picture.
The rest of this board, not drawn here:
- The centre is out of reach, so it is sea.
- The bottom-left and bottom-middle cells are out of reach too.
- Three seas in the bottom-left square make the last cell a dot.
- The bottom-right corner is then out of reach, and the last pool dot finishes the board.
Last corner of a pool Easy
The sea cannot contain a 2×2 block. When three cells of a square are sea, the fourth stays white. Place a dot. That dot is usually the cell an island was still missing. Three seas in a square are enough. You do not wait until the board is full.
The bottom-left square has three seas. The last cell is a dot, with the cream wash and the amber ring. The matching dot on the right is the same rule after the bottom-right corner becomes sea. This picture highlights only the first one. On the blank walk that second dot comes later, after one more unreachable cell.
Nothing can reach it Easy
Each unfinished island can only claim cells within the number of steps it still has left, and it cannot step on sea or through another island. A cell outside every such reach is sea. Shade it. On a small grid this is often a corner once the numbers have taken the cells next to them.
Each 2 still needs one cell. The open neighbours are the cells directly under the numbers. The centre is a step further, and the sea between the 2s blocks the short way. Hint returns the centre, the earliest cell. The same look also sees the three bottom cells. Walking one cell at a time, the next two are still out of reach, and the last corner waits until the first pool dot is placed. Those later seas are not on this figure.
After the centre sea, the corners, and the two pool dots, this grid is solved. Section 2 did it, exceptonly one way out, the easy sentence that this particular grid does not use.
Only one way out Easy
An island that still needs one cell, and has only one empty neighbour, takes that neighbour. Place a dot. Then wall the island, which is walling off a full island. This is still an easy sentence. Many easy grids never need it, because the pool or an unreachable cell writes the same neighbour first. When you do see a single open side, take it.
The 2 has one open neighbour, the cell under it. The cell to its left is already sea. The bottom seas are required: without them, an unreachable cell would be the hint instead. The sentence is the easy one. The window is a medium grid. Some easy grids use this sentence. It is not the usual first move.
A 6×6 easy grid finishes with the 1s, the full islands, the cell between two islands when they face each other, the last corner of a pool, the cells nothing can reach, and this single door when an island has one. Medium adds the count of the cells an island has left, and the shapes of a small island.
Counts and shapes
Count the cells an island can still reach. Dot them when the count matches, and dot a cell every remaining shape uses.
Exactly the cells left Medium
Use this when the easy sentences have stopped. Count the cells an unfinished island can still reach, stepping only as far as the number it still needs, without crossing sea or another island. If that count equals the number of cells it still needs, every one of those cells stays white. Dot them. Hint names one cell. The others in that same look are the same rule. This is what medium adds on some grids. A medium grid that can be finished by listing shapes may show this sentence too. Easy never needs it.
The 2 is finished and walled. The 3 still needs two cells. The cells it can reach are the two in the left column, and no others. Hint dots the upper one. The lower one is the partner in this count, ringed in violet. After the first dot the 3 needs one cell and has one door, so Hint’s next sentence is the single door, not a second count.
From a blank copy of this grid the walk is the sea between the 3 and the 2, two unreachable seas, the single door on the 2, the off-number wall, this count, then one more door on the 3. The whole board is medium.
Every shape uses this cell Medium
Use this when counting the leftover cells is not enough, because the island can reach more cells than it needs. List every way to give it exactly the cells it still needs, connected across or down. A cell that is in every list stays white. Dot that cell, then go back to the walls and the pools. Keep the list small: a handful of cells, an island that needs only a few more. Easy never needs the list. Some medium grids finish with the count and never need it.
The left 3 needs two cells. Sea already sits between the 3s and in the bottom middle. The two shapes are the straight pair down the left column, and the bend through the cell under the number and the cell to its right. Both use the cell under the number. The other two cells are each in only one shape. There is no third shape: the centre does not touch the 3, so every shape enters through that cell.
The right 3 is the mirror, and both of its shapes use the cell under it. That is the same rule in this look. Hint returns only the left cell. Placing that dot changes the board, and the next sentence is the leftover count on the right 3, not “every shape” again.
Medium adds the leftover count, the shape list, or both. Hard adds the sea as one piece, and on many hard grids a one-cell try after that.
The sea stays one piece Hard
Use this when sections 2 to 3 have stopped. The black cells have to end as one sea. Two direct rules, and neither one is a try you leave on the board.
A cell that has no way into the sea, because every neighbour is a number or a dot, and some sea already exists somewhere, stays white. Place a dot.
A cell that is the only bridge between seas that already exist must be black. Unknown cells still count as a way through. If another unknown path joins those seas, this rule does not fire. Shade the bridge. Do not try the white colour first.
The bridge is the sentence most hard grids here use. The stranded corner is less common. Some hard grids use one, some use both, and some skip both and go to the one-cell try. Easy and medium never need either sentence.
The two known seas do not share a side. The 1 blocks the other corner of that square, so every way from one sea to the other goes through the centre. Shade it. This is a direct rule. There is no trial mark. On a blank board the two seas around the 1 come first, and the next hint after the bridge is the try in section 5.
The corner’s neighbours are the 6 and the dot under it. It cannot reach the sea further down. Place a dot. The blank 4×4 does not open on this corner. Its first hint is a one-cell try on the cell under the corner. No 3×3 with one solution names this sentence, so the window is 4×4.
What if the other colour Hard
Use this only when sections 2 to 4 have stopped. Pick one empty cell. Try the other colour in your head, or with a mark you are willing to erase. If that colour breaks the sea, or breaks an island rule, erase it and place the colour that is left. Then go back to the earlier sentences. Try one cell, once. Do not try a second cell inside the first try. Do not leave the failed colour on the board.
Easy and medium never need this. Some hard grids never need it either. On those, Hint stays with the bridge or the stranded corner and never mentions a try. The failure is quiet. Check does not turn the trial cell red. The seas you already trusted stay black. The failure shows up as a white cell that cannot belong to any island, a sea cell that can no longer reach the rest, or a dot sitting between two islands.
Sea breaks an island rule
The bridge is already shaded. Try sea on the cell above it, in the preview colour. Do not leave it there.
The preview sea, or the teal trial dot, is the colour that fails.
Erase the sea and place the dot. The other way, a dot, is fine. The next hints wall the rest of the grid. Do not draw that continuation yet.
- Three cells of the top-left 2×2 are sea, so the corner stays white.
- That white cell touches no unfinished island. The 1 is finished, and the trial sea cuts it off from the 3.
- A white cell no island can own cannot stay. The try stops. Check lists nothing, and the cell may not turn red. The failure is an island rule, not a split sea.
Sea splits the sea
The bottom-right corner is already sea, because nothing can reach it. Try sea on the cell beside the 2.
The preview sea, or the teal trial dot, is the colour that fails.
The dot try is fine. Hint’s next sentence is the wall beside the 2, the cell that shares its side.
- The 2 then has one cell left, and only the cell above it is open, so that cell is a dot. The 2 is finished.
- Walling the 2 shades the top-left corner and the centre.
- The new sea in the top-left has two white neighbours, the new dot and the 3. It cannot join the sea. Check lists nothing on the cell you tried. That sea stays black.
A dot breaks the sea rule
Sea already sits between the two 3s. Try a dot in the cell above it. The dot stays teal. It is not an error mark.
The preview sea, or the teal trial dot, is the colour that fails.
Shade it and erase the dot. The sea try is fine. Hint’s next sentence is a dot both shapes of a bottom island use.
- Each top corner then has only a number and that dot beside it, so both corners stay white.
- Those whites join the two 3s, and the trial dot then touches both islands. A cell between two islands has to be sea. This dot cannot.
- Check lists nothing. Hint’s sentence is still about the sea, because the failed try left cells that could not join it.
Hard adds the sea as one piece, a one-cell try, or both. Some hard grids finish on the bridge alone. Some never name the bridge and finish on the try.
Common mistakes
The first three are breaks Check flags at once. The Hint button waits until the bad mark is cleared. The next two are marks Check leaves alone, while Hint still asks for the real cell. The last is a cell that belongs to one completion and not the other.
The two numbers wash red. The dot stays teal. Check is invalid, and the Hint button waits until you clear the dot. You do not have to finish the board.
Only the centre number washes. The corner 1 stays ordinary, and the dot stays teal. The island is already bigger than its number. The Hint button waits.
All four cells stay black. Check still flags the pool. The Hint button waits. Clear one sea before you ask again.
Shading the cell under the left 2 is not an error yet. Nothing washes. Hint still asks for the cell between the 2s, and it does not ask you to undo this one. In the solution that cell is a dot.
The corner dot stays teal. Check stays quiet while the grid is unfinished. A white cell with no number, and an island that is still too small, are reported only when every cell is decided.
The dashed corner is sea in one completion and white in the other. Nothing turns red. Hint asks for the cell beside the 1, which is sea either way. That ring is the shared cell, not a mark you have placed.
What to play next
Once the 1s and the pools feel quick, move up a setting. Each one adds a new idea.
- Easy1s, walls, poolsStart with the 1s and shade every neighbour. When an island reaches its number, wall it off. Put sea between two islands that would touch. If three cells of a square are sea, dot the last one. Shade a cell no island can reach. When an island needs one cell and has one open side, dot that side.Play Easy →
- MediumCounts and shapesWhen those stop, count the cells an island can still reach. If the count matches what it needs, dot them. If it can reach more cells than it needs, list the ways to finish it and dot the cell every way uses.Play Medium →
- HardOne sea, then one cellKeep the sea one piece: dot a cell that cannot join it, and shade a cell that is the only bridge. If the grid still stalls, try the other colour in one cell, erase it when the rules break, and go back to the walls.Play Hard →
5×5, 6×6, 7×7 and 8×8 come in easy, medium and hard. 9×9 and 10×10 come in easy and medium. Try5×5 easy,8×8 hard, and10×10 medium. Easy grids here use 1s and 2s. Medium adds 3s. Hard, through 8×8, can ask for a larger island.
The daily puzzle is a 6×6 easy grid:today’s Nurikabeorthe same setting in the game. Print packs are at printable Nurikabe. A 5×5, 6×6, or 7×7 sheet holds four puzzles. An 8×8, 9×9, or 10×10 sheet holds two. Large print is one grid.
- GuideLight UpLight every white cell. Start beside the 0s and 4s.
- GuideNonogramsFill cells from the clues. Overlap the long runs first.
- GuideStar BattlePlace stars so rows, columns and regions are exact.
- GuideHashiJoin numbered islands with bridges that never cross.
- GuideSudokuFill each row, column and box with the digits 1 to 9.
- GuideBinairoBalance every row and column with 0s and 1s.
- GuideSlitherlinkDraw one loop. Start from the 0s and the 3s.
- GuideKakuroFill each run so the digits meet the sum.
- GuideMasyuDraw one loop. Turn on black pearls, go straight on white.