The Youtube channel I did a thing got bored line fishing that he convinced himself he could pull a boat using fish. After time-wasting and some of the silliest conversations in the world, he succeeded. He gets them into their harnesses at 12:30 and then the maiden voyage of the fish chariot at 13:20.

Summary: Yes, it works. It takes 4 barramundi fish weighing a combined 16kg to pull a boat at 2km/h for 2 minutes. Then they slipped their harnesses and got away.