Well I could say one thing for sure that you wouldn't be the first or last to have post a thread like this...
One possible reason for this is that your crew was low in fatigue and therefore would not be able to respond in time. Another is the speed at which your boat was going at, though seeing as you didn't assume a crash-dive order this should not be the case. Another would be the depth, this has happened some times to me and to many others, in where they would reach a certain depth and would not be able to even blow-balist.
Or Davy Jones decides to send the Kraken to pull you to the depths (or the locker).
Take in mind that these are all just suggestions and possible veriables to what might have happened. Though you could give more details prier to the incident. Such as what mods were enabled at the time, which off course, would evidently lead to a conclusion that a mod was conflicting with another mod, but this was rarely the case for this type of problem.
By the way, I might not realise what I have wrote so there could be more than just grammatical mistakes.
"Remember, memory is the key..." 