In Game Description
"This area is found in the southwestern part of Gatama Atoll, where the seabed drops off sharply and plunges into the depths of the ocean. The cliff wall itself is speckled with a wide range of corals."
Location and Geography
At coordinates A-7, at a depth of roughly 20 metres down (About 60 ft), there is a large, protruding boulder. If the player gets a saltwater dolphin partner to help them push the rock, they will open up Silent Cavern, thus completing the quest "When the Stillness is Broken" in their notebook. Inside is a tiny tunnel filled with a shoal of Starck's Demoiselle, and the player will have to use their multisensor to find a treasure at the very back of the cavern.
When the player first comes across Blue Cliff with Oceana, a cutscene will play that shows a pod of Humpback Whales swimming near the Cliff.