I found the perfect clock in TechEBlog
Probably all people regardless of their math skills can use it, but I really would love to have this in my classroom.
Each Battleship puzzle represents an ocean with a hidden fleet of ships, which may be oriented horizontally or vertically within the grid such that no ship touches another, not even diagonally. The numbers on the right and on the bottom of the grid show how many squares in the corresponding row and column are occupied by ship segments.
The object is to connect all islands according to the number of bridges so that there are no more than two bridges in the same direction and there is a continuous path connecting all islands together. Bridges can only be vertical or horizontal and are not allowed to cross islands or other bridges.