The tether has to take up this shock load. On the other hand, a small sea anchor only lets the boat drift to leeward faster and to yaw into a broaching position. As the sea anchor size is diminished, the boat reacts increasingly as though it is lying ahull. Rapid backward movement of the boat resulting from too small a sea anchor jeopardizes the rudder. Modern boats with a great deal of windage forward ride better to a sea anchor if a riding sail is used to hold the stern downwind.
Sea anchors can solve a variety of problems at sea.
The singlehander can lie to a sea anchor simply to rest or make repairs in a moderately quiet environment. A boat whose rudder has failed can be repaired while at rest riding to a sea anchor. A dismasted boat can buy time for making a proper jury-rig to continue sailing. The boat overwhelmed by heavy weather can ride to a proper sea anchor while the crew rests and puts it back in order. The sea anchor is a tool to be used when normal seamanship techniques are inadequate to solve the problem at hand.