Sounds like there is a meadows with a draugr village nearby so try to park your ship there or if possible on some rock in the water further out. Build a quick shelter to put your portal down there so you won't have to sail there again. Whenever I'm looking for a swamp biome, I'll always prefer to built my first portal outside of it (meadows/BF) and stay the hell away from there with your boat as the thingies in the water will just snack it it you get too close...
Other than that: Always use best food/armor etc. that is available at this point but you already know that. Once you feel comfortable enough, I'd suggest building a small base (I only set up a workbench and a portal there to tp to my actual main base - but ofc guarded by stake walls for example) on top of a crypt or those giant swamp trees. They are special; if you investigate a bit on that, you'll find building a tree house on one of those is pretty neat.
But as other already said: No walks at night, not even on top of those trees, except you have a roof and solid walls everywhere.
While wandering through the swamps, keep an eye on your surroundings, you may be able to see enemies before they approach you. Try to take them on one by one if possible.
And just to make sure: Sailing at night in certain biomes isn't a good idea either ;)
Always try to repair your boat (don't use a raft) as soon as you can when it gets damaged, just to be on the safe side.