Many of the planets of No Man's Sky feature vast landscapes & ecosystems under the water.
In the Galactic Map, Star Systems that have Planets which have vast amounts of water (50% or more) are labelled as 'Water'.
The oceans hold a great many treasures; but also many hidden dangers. Proceed with caution.
Dreams of the Deep is a secondary mission that immediately begins upon the conclusion of 16 / 16 primary mission or after warping into a new system after achieving the Pioneer milestone (40 warp jumps).
This mission introduces the player to the mechanics of underwater exploration and the Nautilon exocraft.
It follows the logs left by the crew of an underwater Crashed Freighter.