American Dipper
Okay and what’s this, by one of the Lagoon’s little islands? It’s an American Dipper! Wikipedia says they are the only truly aquatic songbird, and this one did seem perfectly at home in the water, swimming down to find worms and snails and things at the bottom — though sadly I didn’t hear it sing.
They apparently love rushing whitewater streams, and are well adapted to cold water and strong currents. Their name comes from the weird little bobbing squats they repeatedly do when out of the water, which are hella cute.