Can a human swimmer use small sail for propulsion?

There was a guy that marketed a survival suit with such about 150 years ago(or there abouts) It's in a book I'm reading ............ I'll check back, he did channel crossings etc in a reclining position & also used a paddle. Jeff.

 

I recommend a large half inflated plastic bag, tied at each end with 2 ropes, that keep the plastic bag at right angles to the wind, that trail back to be fastened to the swimmer.

The following wind causes the bag to form a fat spinnaker shape.

You don't have the problem of keeping the sail upright, and it serves as additional buoyancy in an emergency, as well as adding zero weight to the swimmer. It has the additional benefit of keeping a dry set of clothes inside.

I used this successfully in my escape from Russia across the Barentz Sea to Norway.

 

This would make a great start to a neverending story thread....

 

Rwatson's suggestion is a proven one.
The largest jellyfish, called Portuguese man-o-war, uses the same principle to sail across vast distances, killing and digesting any creatures it encounters.
Lucky for him they have never been observed as northern as the Barentz Sea.

 

Thats true - no man-O-Wars, but I did have to keep a lookout for the Arctic Puffer Fish. It inflates its snowwhite body to float very high, and creates havoc on seals and other marine animals with its poisonous spines.

The Russians during the cold war genetically engineered huge numbers of them with biological transponders to detect surface vessels and shallow operating submarines via their geo-stationary satellites.

Luckily I was wearing a heavy duty neoprene suit, so it was only places where the suit was thin around ankles and wrists that were at risk, and I had very little metal with me.