I feel like this is a game that was meant to be midly satirical in tone and maybe even is inspired by the PS1 007 titles as well, as well as the creatures feeling like they were ripped right from a retro Final Fantasy game, it's definitely a game that forces you to curb your expectations and it works when you actually play it. Now if you decide to upgrade models and such to be more realistic, definitely keep the main story intact as it isn't bad at all. I've seen direct to video films that make this look triple A. Plus the loading screens... you caught onto that.
Thanks:)
The game was originally created for the PS1 "Summer of Shivers" Game Jam, which allocated two parameters for each submission, in that the game in question feature an underwater setting, and incorporate an aesthetic reminiscent of the mid-90s PS1-era. So yes, the resemblance to the early-Playstation style is purely intentional, as is the mixture of both nostalgic and parodic tributes to the era.