Yeah, basically what everyone else said above. Whenever I'm getting ready to go on a boat trip, I make two portals. One portal at my main base(s) and another at the location that I land at. I usually look for an old beat up stone tower to put the portal in, usually on the second floor up and build a roof at the top so that it becomes a good place to put a bed down and get a fire going. Don't get me wrong, I made several trips across the map (and died) without putting a portal down before finally learning the lesson myself.