>>40935805>Why does everything that lives in the water need to be water type?If it's based on a type of animal such that it cannot function out of water for very long, AND it carries that attribute with it, then yes.
e.g. Goldeen and Magikarp are often shown not being able to battle properly outside of water.
Others such as Tentacool are NEVER shown outside of water, whereas some, especially with legs (not tentacles) are able to function fine on land for a time - for example, Squirtle or Poliwrath.
>Does everything that lives on land need to be ground type?No, but again, most things that are based on something that lives IN the ground should indeed be Ground type. If this octopus walks on top of the water, then fair enough it can be pure Fighting. Diglett lives IN the ground. Ursaring walks ON the ground.
>Does everything that floats or flies need to be flying type?Well...yes. That's actually a big problem people have with Pokémon like Beedrill whose animations show it obviously flying in the air, but its lack of either the Flying type or Levitate ability causes it to be inexplicably vulnerable to moves whose animation delivers damage via the actual ground, which visually makes no contact.