I looked up a depth to pressure calculator, at even 1300m, the pressure is 1892.67 psi.

"psi" is pounds per square inch, and a human has ballpark 3000 square inches of surface area.

So to get a (very) rough approximation, picture what would happen if you squeezed a human with 3000*1892 pounds of force. Or try not to picture it, because I imagine it being pretty gross.

MythBusters did this with a realistic (pig?) manikin. Pretty gross, yes.

For anyone that would want to see that: ‘Mythbusters - Compressed diver’ https://youtu.be/LEY3fN4N3D8

Yeah. Reminds me of this underwater pressure awareness training video on youtube from a few years ago: https://www.youtube.com/watch?v=PXgKxWlTt8A (if you're squeemish, don't click that link)

Industrial divers / welders / etc get all kinds of training to avoid that stuff, for good reason.

I'm sure they never imagined this video being paired with an incident like this but wow, their joyful and excited reactions (with no context of the lead up to this experiment) feels really morbid/sick. I realize they were trying to prove a myth and it worked, but still found it unsettling.

You'd have to subtract about 1atm from that, but yes the sudden pressure change would be quite gross.

That said, if divers are slowly "eased in" to the high pressure environment, it is actually possible to equalize pressure slowly and acclimatize. Though 1.3km would still likely be beyond the limits of that https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110125/

The watery bits of the body would be ok but the airspaces like the lungs would rapidly compress to almost nothing.