"Put on your wet suit to dive & swim in the ocean, and even meet new characters!" the company tweeted last week.
The update adds the ability to swim and dive, after which you can donate any sea creatures you pick up to Blathers' museum. You'll also be able to give scallops you find to Pascal -- a sea otter who previously appeared in Wild World, City Folk and New Leaf -- and he'll fork over some marine-themed recipes.
Once you've bought some fetching new swimwear from the shop or Nook Stop, you can hop into the ocean from the beach, pier or rocks, then swim as far as a boundary a few meters off coast. So you won't get lost in the great blue beyond, but you can't check out those intriguing islands on the horizon. If you spot bubbles rising to the surface, diving will give you the chance to meet a new creature.