It’s a one-room shack with a hermit inside: AC0 (chain mail, shield+1, a ring+1, and a 17 dexterity), F6, hp 31, At sword+1 at +2, D4-11, C. He also has a longbow, 17 arrows, and 13 arrows+1, which he will use on anyone attempting to cross the lake. He will see them, 51-150 feet away, 85% of the time.
He shoots from inside the house, gaining AC-3. Also inside is a crude fishing pole, a barrel of salted fish, and a crude table and chair.
Docked to the house is a decrepit rowboat with one oar and five hull points.