I was sailing around looking for swamps, as I hadn't found any with crypts yet. I just pointed my raft south and headed off.
I finally did find some swamps, so I noted it in my map and figured I'd build a nearby base in the dark forest across the channel I'd sailed in on. I could just barely see some trees over there, so hopped back on my raft and headed out.
Did you know leeches can destroy your raft while you're in it? I got about 75% of the way across the channel before it broke.
Fortunately for me, I was near some rocks, and managed to swim to them before the leeches chasing me killed me outright. I still have no idea how to recover my sh*t if I die in the water, and pray I never find out.
I managed to rock-hop my way to the forest I'd seen earlier and started exploring, looking for a good spot to set up my base. I realized I was actually on an archipelago, and there were 8 or 9 small islands all pretty close to each other, all either swamps or dark forests.
I found an abandoned stone tower nestled in an inlet and protected from the tide, so set up shop there. Workbench, bed, some building modifications to secure it against the greydwarves, a roof, and…oh, I didn't have fine wood for my portal. Better go get some.
But wait…fine wood doesn't spawn anywhere in forests or swamps, unless you get lucky and find an old shipwreck (I did not). I guess I better build a boat to go back to some mainland and gather the materials. The karve and the longship both also require fine wood, but I can get by with a raft.
You know what doesn't spawn in forests or swamps? Boars. No boars means no leather scraps, which also means no raft. I had claimed my bed in my new base out of habit, so I couldn't even die and respawn off the island chain. I was literally stuck. I ran all around those islands looking for anywhere I could possibly swim to, but it was too isolated. There was no way I could leave.
I had to call in a rescue mission from one of my buddies after a few IRL days of me looking for a way off the islands.
Anyway, now I always leave an unconnected portal in my home base and carry the material for a portal on my person when I go exploring.
Source: https://www.reddit.com/r/valheim/comments/nd9cab/where_the_fck_i_am_reposted_because_mods_are/