Folks I agree with all of the above posts that a BMS is essential to protect the health of a battery, but ...
I do think in marine applications there is a serious tradeoff between protecting the health of the battery and the health of the boat and crew. There are numerous situations where any boat owner would gladly sacrifice a battery if it means saving the boat. If there is even 1 Ah left and it helps me get the anchor up while dragging onto a lee shore, or get out one last MAYDAY call, then please let me use it. I really can't have the BMS deciding that the health of 1 cell dropping below 2.5 V is more important. So yes, monitor it (perhaps at cell level) and feed it with high quality components (Victron), actively balance it, but ask yourself what your risk tolerance is to the various modes of failure and which failures leave you in more dangerous situations.
One alternative is using a low current BMS to control a contactor's coil voltage and adding a readily accessible switch to bypass the BMS. But I must be able to bypass it without getting out wrenches and diving into the battery compartment.