Ayo /sci I need some help,

I'm planning to build a small, amateur ROV at home using a 3d printer to design a pressure vessel and PVC for the main frame

I'll be printing using ABS, and the main pressure vessel will be a sphere to house a drone flight controller running inav, which is special drone firmware, and 3 cylindrical tubes for cameras, lights etc with a 30mm thick wall. The cylinder will also have between 30-40mm thick walls

The question is: how far will it go down? I'm estimating between 75-125m before anything catastrophic happens, but I happen to live quite far inland and the ocean is a 3 hour drive away, what's a good way to test the pressure vessels?

Also if any of y'all have any good advice would be happy to hear it