Look theres two boat services on the han river and everyone confuses them. The cruise boats are tourist nonsense - overpriced, slow, show you nothing you cant see from the bank.

BUT the water bus is legit transport - 3000w, runs yeouido to banpo plus ttukseom and jamsil. Works like actual public transit not some sightseeing gimmick. Way faster than trudging across those massive bridges when you've got luggage

Daylight hours only though so dont plan evening river hops