The shark on the cover has a belly a baby can press, because it is a soft raised patch built into the board. Inside, the sharks keep failing the test in ways you can feel with a fingertip: one tail is too rough, one fin is too bumpy, and then a set of foil teeth catches the light and that is the one. The little white mouse spends the book in a rubber ring and a rowing boat, which is funnier than it has any right to be.

The structure is what carries a baby through it. One sentence per spread, one new word at the end, repeated until a child who cannot yet speak knows exactly where to join in. Rachel Wells works in flat blue water and hard outline so the animal reads instantly at arm's length, and the fish shoals give an older toddler something to count.

Ten board pages, square and thick, graded from three months by the publisher. It is the ocean entry in a series a family usually keeps buying, and if the appeal here is fingers on texture rather than sharks, Fingertrail Mazes works the same instinct with grooves instead of patches.