1. Try to avoid using rafts... they're crap. They're only good for short navigation along coastlines and never for ocean voyages.
2. Try to avoid sailing at night. Nighttime is when extra beasties come out to play and more importantly, sailing in the dark is a great way to wreck your vessel.
Also, you're in the Swamp biome and there's a certain mob that appears at night there that you really do not want to meet. If you see anything with chains swooping down out of the skies behind you... run like hell. You cannot fight the Wraith at your level.
3. So...
If you stay, then the safest place to rest up in the Swamp overnight is inside a Crypt. If you can find one that is undefended and you can open it, then simply build a campfire just inside the foyer. Explore a bit, but do not attempt to open any of the blocked passageways or else you're asking for trouble. Wait for the dawn.
However, to open a crypt, you'll need the Swamp Key you'll get for defeating the Elder, so consider everything above for later after you have progressed ;)
4. If you cannot stay and use a Crypt, then get the hell out of the Swamp and return to Black Forest or Meadows. If you cannot build a karve, then simply swim. Logout at the moment you run out of stamina and begin to drown. Log back in and keep swimming. Rinse and repeat until you make it to a safer biome.
5. Alternatively, world hop... gather everything you need from another world seed and then bring it back to the one you're currently stuck in.
I wish you success ;)