@xgodkevin
I doubt it was lag, there is a pretty significant difference between latency issues and someone who seemingly has more hit points than everyone else. The cheaters I have run into don't have a god mode, but they take a crazy amount of damage to take out. They also move slightly faster than is possible normally, but not a huge difference you would always notice unless running right next to or behind one.
I know lag exists, but when someone climbs the ladder to your ship, can take two blunderbuss shots and a rifle shot, be knocked off the ladder and still grab back on each time mid air without eating a banana and keep climbing at you, I call shenanigans.
If you run into this sort of stuff, do as suggested above and report them. If they are not cheating they won't be in trouble, but if they are they need to be dealt with swiftly and the best way to do this is via support.