Should I get subnautica or subnautica below zero?

Not really into exploration games like that but I like the ocean and didn’t feel like getting rust and have heard overall positive reviews about this game. I don’t really know the difference between both but would prefer whichever one has more species or animals and if either have them preferably one that has spookier creatures if that’s even a thing. Also looking for the version that may need less grinding. Have no clue about this game honestly but I’m assuming one must take a ton more grinding when it comes to bases and everything