Fleet Deduction Puzzle Generator
A fleet of ships hides in a grid. The numbers down the side and along the bottom say how many squares of ship each row and column holds, and no two ships may touch — not even at a corner, which is the rule that makes the counting informative. Those clues alone usually leave several arrangements, so a square or two is given away, and only as many as are genuinely needed.
What this generator does
Places a fleet at random with clear water around every ship, derives the row and column counts, then gives away squares one at a time until exactly one arrangement fits — and takes back any square that turns out not to have been needed.
How to use this tool
- Pick a grid size and generate a puzzle.
- Use the row and column counts to work out where the ships must lie.
- Remember that ships never touch, so a ship is always surrounded by water.
- Show the answer when you are done, or stuck.
Understanding the controls
- Grid size
- Six, seven or eight a side, each with its own fleet. Larger grids hold more ships and take longer to settle on a single arrangement.
- Seed
- A word reproduces exactly the same puzzle, so the same grid can be set for a group.
Common use cases
- A logic puzzle for a newsletter or club sheet
- Deduction practice that is not a number-placement puzzle
- A puzzle where the rule about touching does most of the work
- Printing a set of puzzles at one size
- Demonstrating a puzzle proved to have exactly one answer
How this generator works
The published grid is solved again from its clues, counting arrangements rather than trusting the construction, and is only shown when the count is exactly one. The answer is then taken apart independently: the ships are traced out and their lengths compared against the fleet, the counts are recounted from the grid, and every diagonal pair is checked to make sure no two ships meet at a corner.
Randomness and fairness
Ship placement comes from the browser's secure generator. A seed reproduces the same grid exactly — that path is deterministic, not cryptographic, and exists so a puzzle can be shared.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Six to eight squares a side. Larger grids take long enough to settle that they are not offered.
- The fleet is fixed for each size rather than chosen.
- Difficulty is not graded — a grid needing no given squares can still be harder than one needing two.
- No hints beyond the given squares; the answer is shown whole or not at all.
- Nothing Fleet Deduction Puzzle Generator produces is kept once the page closes — the seed is the only way back to the same output.
Privacy and your data
Grids are built and checked in your browser. Nothing is transmitted or stored.
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