“You Must n’t Swim…”

You must n’t swim till you’re six weeks old,
    Or your head will be sunk by your heels;
And summer gales and Killer Whales
    Are bad for baby seals.

Are bad for baby seals, dear rat,
    As bad as bad can be;
But splash and grow strong,
And you can’t be wrong,
    Child of the Open Sea!