under the water.

Suddenly, Tom heard the strangest noise up the stream; cooing, and
grunting, and whining, and squeaking, as if you had put into a bag
two stock-doves, nine mice, three guinea-pigs, and a blind puppy,
and left them there to settle themselves and make music.

He looked up the water, and there he saw a sight as strange as the
noise; a great ball rolling over and over down the stream, seeming
one moment of soft brown fur, and the next of shining glass: and
yet it was not a ball; for sometimes it broke up and streamed away
in pieces, and then it joined again; and all the while the noise
came out of it louder and louder.

Tom asked the dragon-fly what it could be: but, of course, with
his short sight, he could not even see it, though it was not ten
yards away. So he took the neatest little header into the water,
and started off to see for himself; and, when he came near, the
ball turned out to be four or five beautiful creatures, many times
larger than Tom, who were swimming about, and rolling, and diving,
and twisting, and wrestling, and cuddling, and kissing and biting,
and scratching, in the most charming fashion that ever was seen.
And if you don't believe me, you may go to the Zoological Gardens
(for I am afraid that you won't see it nearer, unless, perhaps, you
get up at five in the morning, and go down to Cordery's Moor, and
watch by the great withy pollard which hangs over the backwater,
where the otters breed sometimes), and then say, if otters at play
in the water are not the merriest, lithest, gracefullest creatures
you ever saw.