They get to know each other, and Amos, upon reaching his home shore, promises Boris that if he can ever help him with anything, that he will. It takes them a week to get home, during which Amos learns to eat plankton somehow (maybe since he's a mouse, they're big enough for him to see? But how would he get enough of them to eat?) and apparently only misses 'fresh, unsalty water' instead of simply dying of thirst.

Upon receiving Amos's explanation of his origins, Boris agrees to carry him home, fascinated to get to know such an unusual creature. Luckily, this happens in the middle of a whale pod, and a whale named Boris comes by the next day and marvels at the unique animal in the middle of the ocean. At any rate, he is some kind of natural-born boat-builder and sailor, and instead of practicing sailing near the shore for a while, he just immediately heads off into the middle of the ocean, where he gets so wrapped up in navel-gazing that he falls off the boat and into the ocean, never to see the boat again. Maybe, since he's a mouse, he doesn't expect there to be many fish of the size he can eat. It's unclear where he learns how to build a boat or sail, although he does seem (from the perspective of a layman such as myself) to take important things with him, such as 'wood in case repairs should be necessary' and 'a needle and thread for the mending of torn sails.' Oddly, he doesn't seem to take any tools for fishing, though you would expect that to be a major source of food on the ocean. This is an odd story, but I suppose that's to be expected from the author of 'The Amazing Bone' and 'Sylvester's Magic Pebble.' A mouse named Amos, who lives by the sea, decides to build a boat and go sailing in the ocean.

Amos and boris