Sea Battle strategy: how to find and sink every ship

How the Sea Battle ship game works

Sea Battle is the classic hidden-fleet guessing game. Each player has a secret fleet on a grid of sea, and you take turns firing at squares of your opponent's sea. Sink every enemy ship before they sink yours and you win. People have played it with pencil and paper since the early 1900s, calling out shots like "C5!".

In Sea Battle on PlayTrova, each fleet sits on an 8×8 sea and has five ships:

• Carrier: 4 squares
• Cruiser and Submarine: 3 squares each
• Destroyer and Patrol boat: 2 squares each

That's 14 ship squares hiding among 64. Ships are always straight, and they never touch each other, not even at the corners. A splash means a miss and a flame means a hit. When every square of a ship has been hit, it sinks and its name is announced. In the default game a hit lets you fire again; the Classic option switches to strict turns, one shot each.

Hunting strategy: search in a checkerboard pattern

The most common beginner mistake is firing at random, or sweeping across the sea one square at a time. There is a much faster way. Imagine the sea is a chessboard and only fire at the dark squares: every other square, like a checkerboard.

Why does this work? Every ship is at least two squares long, so wherever a ship lies, it must cover at least one dark square. Only 32 of the 64 squares are dark, so by the time you have fired at all of them, you are certain to have hit every ship at least once. Usually you find them much sooner.

• Start near the middle. More ship positions pass through the middle of the sea than along the edges, so early shots there are more likely to hit.
• Spread your shots out. Rather than working along one row, scatter your dark-square shots around the sea, then fill in the gaps.
• Don't forget the edges. Because most hunters search the middle first, the last ship is often hiding along an edge or in a corner.

How to finish a ship once you hit it

A hit changes everything. Stop hunting and switch to target mode: finish that ship before you fire anywhere else. In the default game every hit gives you another shot, so finishing a ship quickly can win you a whole string of extra turns.

1. After one hit, try the four squares directly above, below, left and right of it. Ships are straight, so the rest of the ship must lie in one of those directions.
2. After two hits in a line, you know which way the ship points. Keep firing along that line.
3. After a miss at one end, turn around and work along the other end of the line.
4. When the ship sinks, go back to your checkerboard hunt.

Listen to the announcements, too. Ships that have only been hit are never named, but sunk ships always are. Say you have three hits in a row and nothing has sunk. A 3-square ship would have sunk already, so this must be the Carrier, and there is exactly one more square to find at one end.

Use logic to rule out empty water

Good players win as much by knowing where ships can't be as by guessing where they are. Because ships never touch, PlayTrova marks every square around a sunk ship with a little dot. Those squares are certainly empty, so skip them.

Next, think about which ships are left. If only the Carrier is still afloat, a pocket of unknown water three squares long can't hold it, so ignore it. A single unknown square boxed in by misses or the edge can't hold any ship at all, because even the smallest boat needs two squares in a line.

Here's a trick for later in the game. Once both 2-square ships (the Destroyer and the Patrol boat) have sunk, every ship left is at least three squares long. Now you only need to fire at every third square in each row, moving the pattern along by one square on each new row so your shots form diagonal stripes. That covers the sea with even fewer shots. It's exactly how Sly Fox, the third computer character, hunts.

Placing your own fleet

In PlayTrova's Sea Battle, fleets are placed for you so games start quickly, and the game makes sure your ships are straight and never touch. You can't drag ships around, but you can tap Shuffle my fleet as often as you like before your first shot, as long as none of your ships has been hit.

So what should you look for when you shuffle?

• Ships along the edges and in corners tend to survive longer against players who search the middle first.
• Small ships are your best defenders. A 2-square boat is the hardest target on the sea and is often the last one standing.
• Avoid a fleet that looks like a pattern, such as every ship lined up neatly in rows. Human opponents notice patterns quickly.

Playing the paper version at home? Then you choose every position yourself. Mix horizontal and vertical ships, use an edge or two without crowding every edge, and change your layout from game to game. Friends who play you often will start to remember your favourite spots.

Practise against the computer, a friend or the daily fleet

The four computer characters each search in a different way, which makes them a great ladder to climb:

• Rookie Robo fires almost at random and often forgets to follow up a hit.
• Clever Cat hunts at random, but once it hits a ship it doesn't let go.
• Sly Fox sweeps the sea in a checkerboard-style pattern and finishes ships neatly.
• Grandmaster Owl works out every place a ship could still be hiding and fires where one is most likely.

None of them cheat: they only know where they have fired and what they hit, just like you. Against the computer you also get three hints per game, each showing a good shot when you're stuck.

For a pure test of your hunting, try the daily Sink the fleet challenge. Everyone hunts the same hidden fleet that day, and you try to sink all five ships in as few shots as possible. 14 shots is perfect, and Grandmaster Owl needs about 29 on average, so anything under 30 is excellent.

Prefer a real opponent? Take turns with a friend on one device (fleets stay secret on a shared screen) or send a link and play on two devices. There are more ideas in our guide to games to play with friends online.

Common Sea Battle mistakes

• Firing at random instead of using the checkerboard.
• Wandering off to hunt somewhere else before a hit ship has sunk.
• Shooting at squares next to a sunk ship or diagonal to a hit, which are always empty.
• Forgetting which ships are left, and searching gaps that are too small to hold them.
• Searching only the middle and leaving the corners until the very end.

Sea Battle is a quiet way for kids to practise logical thinking. For more games like it, see our guide to math games for kids or browse our learning games and puzzle games.

Frequently asked questions