Hide and Seek, Seek and Find

As you're patrolling near a small grove of sea grass, some unidentifiable but disturbingly large shape passes overhead, blotting out what little light is trickling down from above. Quickly weighing your options, you decide your chances are better with anything that might be lurking in the sea grass than in what looms above you. You snap off your light and with a few quick swipes of your fins you glide into the shelter of the grass.

Long moments pass, before the sea above lightens again. You wait a bit longer just to be sure, and then snap your light back on.

In front of you, nestled in the grass, rests an improbable contraption that is at once both infinitely impractical and also immediately recognizable as a bicycle built for a fish. Two fish, actually--it's a tandem.

This Perch kid must have dropped it here. You pull it out of the weeds and take it with you.

You got an item: Bicycle built for two fish

Part of the Go Fish quest.
Found in the Porcelain Bay area.