I don't think anchors exist unless they were just added.

A boat will not "drift" if you get off it. If you are the only one on the boat or playing solo the boat will stop as soon as you jump off it.

Out to sea and moving? Boat will stop dead the moment you jump off. Next to land it won't drift away or anything.

The only worry with a boat is with the waves banging it against stuff. The things you put around it may actually have broken the boat.

"Most" of the time they can be left without issue, but to be safe I find it better to pull into shallow areas and break the boat and carry it or put it in a box.