Unlocking new in-game music tracks:
After you go to the Abyss for the first time, you'll unlock the song "Benedictus (Hayley Westenra)"
You can now select this song to play for future dives.
View Staff Credits:
When it's sunset in-game (after 6pm), sit on the deck chair. Look out over the horizon to view a special cut-scene with Staff Credits.