Crabbing involves tension and force. I went crabbing in Oregon last summer, and it was really fun! First, you drop your net basket off the side of the boat and let it sink to the bottom. After a period of time, you haul on the net basket rope to bring it back up. Because you pull at an angle, the force has both a vertical and horizontal vector. Tension is also involved because the rope must be kept taut, otherwise the crabs will be able to fall out of the basket. Since the rope touches the side of the boat as you haul up the crabs, there is friction involved too. I had to apply a lot of force to haul up my basket...I never knew crabs could be so heavy :)