Naval landing is not the safest way to start new biome, especially swamps.

Here is my algorithm of starting swamps(way too safe because I play ironman):
0. Always use poison resist potion while in swamps.
1. Scout several swamps reachable on foot.
2. Find some turnip seeds.
3. Build base near swamp in the forest. It is perfect if there will be mountain and plains nearby.
4. Farm some Draugrs and cook sausages.
5. Find crypt and build shelter nearby. You need safe crypt without inside spawn point close to entrance.
6. Farm some iron and craft iron armour. Put all iron in armour upgrades.
7. Now you may go deeper into swamps.
8. Clear all spawn points on your way. Move there, destroy single spawn point, run away, destroy pursuers, repeat.
9. Clear all abominations on your way. They are very durable but their hits are very weak. Spend all stamina to deal damage, walk around indestructible tree to restore it, repeat. Drink healing potion if needed.
10. Farm enough iron to craft/upgrade/build whatever you need.
11. Kill Bonemass using the same tactic as vs abominations.

If you aren't sure in your skills you may terraform swamp. Raise ground. Chop trees. Build workbenches to block most spawns. Build shelters everywhere. Build roads for cart. That's very time consuming but if you are on day 137 you obviously don't hurry.