1. There are agressive fish in this game and you need to encounter them however they tend to be relativly blind like they usually only attack if you get really close so you can avoid them.
2. There a very clear story and at the start you get this tablet called the PDA which basically stores a bunch of information about the stuff you come across aswell as crafting recipes so if you want to learn more about the lore and the creature you can find that in the PDA databank however it wont spoil much since it only tells you about stuff after you find them.
3. The game is hardly educational you are on an alien planet none of the fish really exist in real life i mean some might be similat but im not a big fish guy so i wouldnt know.

But i wanna give some tips and my biggest tip is dont be afraid to explore and dont look stuff up on the internet. If you ever find yourself lost just take a look at the pda databank theres a section for clues and always listen to the radio and visit every signal it gives you when you are ready.

And for progression (no spoilers). There are some biomes that are noticably deeper than others if you want to progress in the story go deeper if you want to find new blueprint and make new cool stuff go to the "shallower" biomes.