Keep in mind that's likely not related to the dB sound pressure level in air that we're all familiar with. dB is a logarithmic ratio to pressure to a reference. In air, that reference is 20µPa, acoustic pressure in water typically uses a different reference (1µPa). There is also an adjustment of 36 dB to account for the higher impedance of water. So 235 dB in water is roughly 173 dB SPL -- still loud, but many orders of magnitude lower.

[0] https://fas.org/man/dod-101/sys/ship/acoustics.htm

This is what you can expect https://www.youtube.com/watch?v=sCmyZYYR7_s&t=90s

This diver was near a sub base for training.

Comments say this was very likely not a sub‘s sonar.

The only saving grace is that they only use it as a last resort since sending out that kind of noise would let everyone in that hemisphere know exactly where you are.