I'm not sure what happened, but common things to look out for are seals that are too loose, hair trapped under a seal and extends beyond it and then actual defects.
To get soaked would be a pretty major leak in 35 seconds, I can't imagine something like that happening in a pool that fast without a large tear or visible hole, or zipper that's unzipped.
I might define soaked differently.
So, make sure the seals are solid and fit you properly. The single biggest mistake you'll find in rental drysuits are the seals, expecially the neck seal. That seal takes a lot of abuse due to it's being stretched over your head each time and many people aren't aware of how to properly don that seal and just pull it over the head when they put it on and off.
Latex seals better in many cases for those with bony or real thin necks wrists, neoprene may be tougher but is more likely to leak or not confrom to odd shapes.
Hope you have a better class next time, I assume you found what caused the leak? What part of your clothes got wet, most wet I should say. That identifies the source.