Originally posted by Suzaku:

If your respawn is still back at base, you could change the current portal's name to something unique, die nearby where it won't be hard to retrieve (maybe jump off something nearby and die to fall damage), respawn at base, make a new portal with the name of the portal near your corpse. Bring nails with you to your corpse to make a new boat and continue your adventure.

Or make a new character, have it join your world and run to base to double-check the portals are as they need to be, or for it to make a new one.

Thanks for tip. Unfortunately I had quite a few stop over at locations on my way, the last one on an island not connected to the island with my main base. Maybe I should try your second tip and create a new character.
I had a save while I still was on my boat travel (saved by quitting the game), but right after arrival there was a "the forest is moving" event, and the game obviously makes a save after such events, because when I closed the game's window from desctop after giving up finding the nails,, the reload did not bring me back to my boat travel, but to a point right after "the forest is moving" event.