Question

When you row a boat in the direction opposite to the wind you have to put in extra effort

Answer 1

When you row a boat in the direction opposite to the wind you have to put in extra effort because you have to overcome the wind as well as natural resistance of the water.

Answer 2

There are couples of reasons for that. Rowing a boat in wind needs one to overcome the wind resistance caused by boat hull & by the body.

Rowing the boat in wind usually indicates that you are rowing in waves as well so that friction created by the waves will serve like a brake & dampen the forward momentum of boat easily.