You are searching for the disabled submarine "Chrysalis" by diving with a submarine of your own, use the navigator to travel to points of interest. This game was designed to explain itself, so don't be overwhelmed by the UI!
Sounds edited from other projects: https://scratch.mit.edu/projects/550000672/ https://scratch.mit.edu/projects/607186476/ https://scratch.mit.edu/projects/1109476338/