How to I make water like Flood escape 2?

I'm making a game that involves water but I want to make it swimmable just like in flood escape 2, like how you press space to swim up and shift to go down, but I couldn't think of any ways to do it.

Try playing around with Body Position and see if that works for you, you can also code a water similar to terrain water but that requires more tweaking of body position

Lets say Water is a parts position

local Water = Vector3.new(0,5,0)


local BodyPosition.Position = Water --will set it so that it floats