if you have trouble then plan it out.

figure out where the crypts are and find a short path from a non swamp biome to it.
if its long or indirect then terraform with the tool option that doesnt take stone.
clear out the monsters that are in aggro range with bows and maces (maces work very well in the swamp since most mobs there are weak to blunt damage)

if the path is still to dangerous or long you can also make a small hideout on one of these trees to regain the rested buff and heal. these trees are invincible

aside from that you can also use the entry of the crypt as a safe zone.
if you have trouble within the crypts than craft some stagbreakers (they only require deer trophys, bones and core wood if i remember correctly)
stagbreakers allow you to hit the enemys and their spawners without having to enter the room (leave a little bit of the mudpile so that they cant hit you)

and always keep your objective in mind and make it quick, a lot of deaths usually come from people wandering aimlessly and then stumbling into increasingly worse situations