some idea for a potential final boss fight:
given that we saw the bio canisters, there might be some mutant monster down there that is engulfed in flames nonstop, potentially the weird blue flames-
obviously has to be hurt by water (duh) and every once in a while, the beast like focuses power and then releases it on a big exploion, flames literally flying everywhere. you k now, like when the doors blow open, just that that the fiee blast is away from the beast in a circle.
then obviously have it walk around a bit left and right, sometimes spewing flames towards your direction (can be blocked by the water shower thing).
and maybe have some mechanism there. caus, you know it's the final boss and he is in undying blue flame and whatever, so your tiny water thrower doesnt have the water pressure to kill his flames off.
so there might be a big water reservoir somewhere upstairs, which by some platforming or other lengthy methods you have to release, so it flows down into the conveniently shaped area where the boss is and basically drowns the boss.
so even if the flames dont really die off, they cant ignite again cause if they do, the surrounding water will put them out again.
boss defeated, world saved, find some good story on why there happened some weird mutant biogenetics accident that turned the random animal into some fire god beast :-)
seriously, give this game a boss fight and some badass music and it's amazing! :-)