This spacious but shallow cove is near Cross Rift in eastern Ciceros Strait. It is populated by small fish, including Japanese Jack Mackerel, Teardrop Butterflyfish, and Oriental Butterflyfish along with a pair of Red Stingrays swimming near the entrance, and a colony of mediterranean monk seals. It is aptly named, as the seafloor here is covered in stunning white sand. You can go ashore in this area, and on the small beach, you will find more Monk Seals, some driftwood and, more mysteriously, some wooden planks that look like they possibly came from a ship.
White Cove

White Cove as seen while on shore. Several seals can be seen.

In-game, your notebook describes this area as follows:

Located in the East of Ciceros Strait, this rounded area of shallows looks like it was cut out of the surrounding rocks. Its beautiful white sands are home to the many Mediterranean Monk Seals in the area.

A programming shortcut concerning the aesthetics of the shore area was taken. While on land, the above-water part of the entrance to the White Cove looks identical to the above-water section of the entrance to Triton Cove.