Aboat would like to cross a river in the most direct route. because of a current, the boat must aim upriver in order to directly cross the river. to the nearest degree, what is the angle the boat should head upstream?

The angle that the boat must follow for it to be able to head upstream successfully should be 45 degrees from the current at which it is crossing. This is exact protocol that is done or learned by rescuers. In able to swim across a current, you must not invest your energy in heading towards it but rather move in a semi-perpendicular direction from it.