One of my first games, and an amazing experience as a child - having to use the lights when daytime switched to nighttime (and when diving to darker depths, collecting "waste" (resources), trading, and all at a miniature scale! Also, the CGI cutscenes and renderings when entering harbors put you neatly into the game world, and the music in this game - very fitting for exploration in this underwater setting, and I still listen to it sometimes to relax :)
I really hope this little gem of a game can be brought back, despite being very niche - maybe even with the somewhat-spiritual successor "Deep Fighter" some day?