Almost all of the sailing I have done has been single-handed. At first my only concern was to stay attached to the boat, but then contemplation of being overboard intruded into my conciousness - how was I to get back aboard?. I made and tested a boarding ladder that was accessible from the water. I think it is essential that a single-handing sailor be tethered to the boat and that if the tether enables the sailor to go overboard there has to be means for getting aboard again. This goes for sailors whose crew is not fully capable of handling the boat.
Trailing a line is a nice concept, but what if you miss the line? I can remember reading a single-handed cruising tale where the skipper was becalmed in the doldrums and went swimming using a trailing warp to get back to the boat. A puff of wind filled the sails and the skipper missed the rope. He swam methodically toward his boat and eventually caught it. The mere thought of being a thousand or so miles from land while my sailboat indifferently sailed away gives me the chills. Survival while single-handing needs to be as foolproof as possible and practical.