It wouldn't be too hard to have a drogue attached to the painter with a rolling hitch or something simillar that could be tucked in near the cleat. When you cast off the dink the drogue would hit the water and stop it from sailing away. That might give the reluctant swimmer a chance to catch up. The down side of that is I like to have a floating painter to minimize the chance of it getting into the propeller but it would be advantageous for a drogue to sink. Having a few feet of nylon line between the drogue and painter might fix that.