About crew endurance

[Vipper]

I have two questions, may i ask? Does crew member will regain endurance somehow? And how it is possible, that after days of sailing over north sea my crew will lose almost no endurance only just a little bit and then, after hour hiding, maneuvering and fighting they are losing almost all of endurance and i have a boat full of exhausted human wrecks barely able crawl back to home dock?