I don't think he means offshore (off-bank?) I interpreted it was up-shore (or down-shore(-bank)).
I forgot to mention it by the way but yeah assuming there's a settlement nearby because you find a fresh water source -- particularly a big one such as a river -- seems completely in-the-ordinary to me. All civilization is built on the accessibility of fresh water. If you're lost in the wilderness and find waterflow your best survival bet is to follow that flow downstream because that's where chances are the highest you'll find other people or their dwellings.
