The furry river denizen tolerated the reprimands that came with their oars a few times, then turned on them when things got too far, the Dartmouth, official publication of the Hanover, N.H.-based college, reported Friday.
No one was injured, but the incident, which occurred 7 miles upstream from the crew boathouse, rattled the nerves of all involved, the report said.
The otter jumped into the river to play in the wake of the coach's launch, said varsity coach Scott Armstrong.
Volunteer coach Todd Pearson and coxswain Kate Johnson accompanied Armstrong in the launch.
Armstrong turned off the motor to avoid injuring the otter with the propeller. The otter then immediately tried to board.
Armstrong grabbed a wooden paddle and attempted to fend off the animal, but the opponent outmaneuvered him and came aboard.
The animal then began to lunge and hiss viciously at the coaches.
After a stand-off, the otter went for the second varsity boat that was in the process of turning around. The boat immediately fled.