Seaspray is a fat otter pup. He is sable-furred all over and has black eyes. He commonly wears a smock, except when swimming. He made himself a tiny slingshot out of wood and a strip of cloth, and uses pebbles as ammunition. He nods off during Abbey School, but when the word, 'Dismissed' is heard, he will have mysteriously awaken and gone off to play or swim. His brain is full of plots for mischief, which he plays out with his best friend Rilla the Mousemaid. When he and Rilla escaped from the Abbey Kitchens, where they were working as a punishment, the two were the first to discover the Message carved into the Abbey Walls.