I take basically spares for everything. Why? I get such small amounts of time for "stick time" and the safe water way is at such a distance to get to that if something does breakdown I prefer to fix right away and try and salavage some run time.
The wife has commented that going submarining in our household is a bit like owning an Indy team. I have actually thought of building a 1/12 scale or larger RC Prime mover and race team trailer, with the trailer holding my Thor Alfa and spares. I had a quick cold shower and came back to reality.
Typically I think we do take more to the lake than skimmer drivers - yet its amazing to see how many skimmer captains have a syringe in their tool box and use it to routinally bail out loads of water at days end! I'd like to think that collectively our engineering skills are better-as a sub the same situation would mean a swim!