Below the Grotto there lurks an underwater area called The Abyss. You can get to it in one of two ways. If you prefer, you can teleport directly to the bottom. Or, you can walk to the back of the Grotto and pick up a free diving suit, then jump into the water.
This is a great place to get away. Relax or walk around and enjoy the underwater creatures.
For another underwater experience, also check out the Secret Spa, located on the other side of the region.