I want to test a Humanoid's ability to swim, but currently we can only completely submerge the Humanoid in water just like the Swimmer. Is it possible to define different density and viscosity values for parts of the environment? Also, I was unable to confirm if the Humanoid can swim in water without touching the ground. I set density=5000, viscosity=0.1, gainprm=1.1, stiffness=100, but have left gravity enabled for now. What parameters do I need to change to allow the Humanoid to move with the force generated in water?