How to stop players from ascending in water but make them slow?

Basically like Booga Booga on Roblox, you cant climb up water, so you use the rope to get on sky island. Except i want people to be able to swim in MY game. And if you have to take away swimming then its alright as long as I CAN FINALLY STOP PEOPLE FRM GOING UP WATER PILLARS!!!!!!

Different materials have different weights, for example Concrete and Granite make you sink instantly, and wood and plastic are lighter. If you change the material of the HumanoidRootPart, and experiment how you swim in water with the different materials, you could find one where your character sinks but you can still swim around/up