Pearl oyster

The pearl oyster is a sea creature you catch while swimming in the sea (dive where you see bubbles). Look for a small shadow. In the northern hemisphere it is around all year, at any time of day. It can only appear after you have caught 20 sea creatures. Nook's Cranny pays 2,800 Bells.

A small shadow around all year, after 20 catches. It moves at a moderate pace and sells for 2,800 Bells, a tidy sum for such a small find.