How can I simulate pressure, calculate altitude or simulate the triple point of water in UPBGE?

How can I simulate atmospheric pressure or water pressure on the player in UPBGE? The player will move a fair bit slower in water, and lots slower in lava.

How can I also simulate objects breaking under pressure without Cell Fracture or Geometry Nodes and with just Python?

Also, how would one calculate altitude from game terrain (for example, climbing up a steep hill, or going into a sea trench)? This would be separate from velocity.

Now for something crazy. How would one even go about simulating the cyclic nature of water at its triple point phase (freezing and boiling at the same time) in UPBGE? That would be cool to watch, but maybe a little too much, and would really kill performance, and might be better off for EEVEE Next…

I do not know why you need this, but you can simulate such effects with a huge number of options - starting from checking with a radar or a beam how deep the player’s collider plunged into the water, or for example using the action of force fields to simulate the destruction of objects under pressure - you need to create a set of their parts - and add these details when destroyed by combining their arrangement to calculate the height of the landscape take the height of the player on the Z axis -
hight = own.worldPosition.z
about freezing or boiling - why and for what is it necessary? just to see? or for a specific stage of the game? or so that no one will ever answer your question on this forum?