Poison resist potions are the single most important thing for the swamp. They have to be taken BEFORE you get poisoned so you want to bring a stack and always have them going as a single dose of poison from swamp level critters can do 70 damage from no star stuff without poison resist. Which means sitting by helplessly as you die if you don't have poison resist going. With poison resist it's knocked down to less than 20 damage.
Aside from that park your boat safety and bring portal supplies. When you need to unload/resupply/repair (non-ore stuff) pop home via portal. All your scrap iron should go into your boat untill you have a ton/cleared the area then you can sail it home. The safest spot for portals is going to be on top of the swamp crypts.