Deep-sea diving was introduced to the game during the Summer Update: Wave 1. It gives the player an opportunity to collect deep-sea creatures that can be donated to Blathers at the museum.
How to Deep-Sea Dive
First off, you’ll need to buy a wetsuit from Timmy and Tommy. They cost 3,000 Bells and come in a variety of colours. You can also buy a Nook branded wetsuit at the Nookstop for 800 Nook Miles.
When you’ve bought a wetsuit, you’ll need to equip it before you can head into the sea. You can enter the sea from the beach, rocks or the pier. Press A when you’re near the edge of the water and you’ll swim in. To swim, you’ll need to press A repeatedly to keep moving. To exit the water, simply swim up to a beach shore.
Finding Sea Creatures
To find sea creatures, you’ll need to keep an eye out for bubbles floating to the surface. When you’ve found some swim over and then press Y to dive. Some of the creatures will swim away from you, but you can adjust your positioning under the water.
When you’re beneath the water and directly above the creature, your character will swim down and bring back up a sea creature! Make sure to always donate the first of different species to Blathers. Some sea creatures will not move when you dive for them, whilst others will try to swim away from you. The speed of the sea creatures vary from species to species. Some will be incredibly fast and the best way to catch them is to swim above water until you’re right on top of the bubbles before you dive for it. This can take a bit of practice, but luckily, they will not despawn when you fail to catch them before you lose your breath and have to come up for air, so you can try again.
Finding your First Scallop
When you find a scallop for the first time, Pascal the Otter will spring up behind you. He’ll ask for the scallop and in exchange give you a DIY recipe that requires Pearls. Pearls are rare but can be found on the ocean floor. Pascal will also exchange pearls for scallops. You can trade with Pascal once per day, but for him to appear you need to have found a few scallops during the day. The DIYs he gives will be a part of the mermaid set.