Teamwork
If the fishermen tried to reach over, they were well aware that doing so put them in jeopardy of being swept away by the powerful current, as well as putting themselves at risk of being injured by an angry bear. However, they were unable to simply release the cub into the wild.
In the end, they reached the conclusion that they needed to have faith in the fact that the cub, if given the chance, would work together with them in order to save itself from certain death. They purely and simply hoped that nobody would sustain an injury during the procedure.