Thanks all. Lots of good tips. Kind of glad swamps actually are hard and I'm not just hopeless...

The reason I picked that swamp was that, after sailing for weeks, it was the only one I'd seen that had crypts I could spot. All the other swamps I'd found were narrow stretches on the coast (that map had a lot of that sort of thing. Black forests were the same way) and it didn't seem likely they had many crypts, or any at all.

I also didn't know ship landings caused that much attention. I'll keep that in mind.

I think I'll go for bronze armor this time. Never tried it, so it's kind of about time.
And then massively overprepare next time I start a swamp.