Do you like sailing? Are you fond of the ocean? Ever wanted to live on it? Now read all of that in the tone of an upbeat American infomercial, followed by a flat, 'too bad'. There are no boats in Sons of the Forest, not yet anyway. But its fans are an inventive bunch, so that isn't stopping them from sailing the seas (or, more accurately, surfing).
As said by u/Repelation on The Forest subreddit, "maybe we don't need boats after all". They attached a short nine-second clip where we can see them awkwardly walking along the top of a shark as it moves across the water, occasionally jumping to avoid falling and being caught by a... well, shark.
The downside to a shark boat is that you can't tell it where to go. It's not like you can paddle a shark, and there's no way to lure it to the shore while you're on top of it. Once you're riding it, all you can do is wait and hope it takes you where you want to go, and then make a quick dash away to avoid becoming its lunch. Or, by the time you get to the shore, its midnight snack.
The Forest did have boats - it had a small raft, a large raft, and even a houseboat for portable seafaring shelter. None of these are currently present in its sequel, Sons of the Forest, but it's still in early access, so that could change at any time. For now, you'll have to get creative if you fancy exploring the ocean, not that there's much to see.
Using a shark, however, you might be able to escape some of those pesky monsters and cannibals, which is a decent reason to find one to hop onto. According to the comments, you can find one "near the raft where you get the 9mm" and "in the rebreather cave". And as another commenter says, hopefully, we'll be able to tame them properly one day - I think I'll call mine Lenny.