Deep-sea creatures (海の幸, seafood) are a type of catchable creature introduced in New Leaf, just like bugs and fish. The player catches them by swimming in the ocean and diving down when directly above a shadow, or swimming underwater. Shadow sizes range from as small as the mantis shrimp to as large as the spider crab and giant isopod.
As like fish and bugs, they can be donated to the museum upon talking to Blathers, who will then put them on display in the deep-sea creatures exhibit.
Some of the fish in previous Animal Crossing games are now deep-sea creatures. These include the octopus, crab, and lobster.