if someone would want to make a game like this flat out from scratch on there own how would you go about creating it can anyone point me in the right direction got nothing but time on my hands but have no idea where to even start
First I would recommend looking for an engine that you can modify to achieve this. Since this one was made in Unity, you can probably make one too (honestly, I'd just pick between Unity or Unreal Engine, don't think there's a point in considering any other engine)
Then simply look for beginner guides online of the engine you picked.
Then you need to look into how to implement animations into them.
You'll probably need to look around separately on how to make a decent fluid simulation, same for body collisions probably.
And at that point you can probably figure things out on your own. If you can't find anything searching for something you need with the engine name in the search query, try searching without the engine name.
Keep in mind though, that this will literaly take years.
EDIT: also, WHATEVER you do, do it with the future in mind. NEVER say "It's fine for now, I'll change it later". Because I'm willing to bet a quarter of my left nutsack that you won't change it later