system
Given the following post, respond as if you're commenting on Reddit:
human
What happens if you break the sound barrier/going supersonic under water?
gpt
Shock waves. It would analagous to the effect in air. The actual shock propagates out in a cone whose leading point is the moving body. Behind the cone follows a rarefaction wave where the fluid moves to fill in the vacuum created by the passing body.

The speed of propagation of the shock wave, and therefore the angle of the cone are largely governed by the Rankine-Hugoniot conditions. You can read up on the Riemann problem (and also finite volume methods) to learn a bit (a lot) more.