Like Chris I thought that this had already been done and the result was a complete stop.
I found this from "Riddo" on P4 of this thread:
viewtopic.php?f=71&t=31296&p=125596"Last weekend I went out sailing with my Nephew and his mate on the TI. It was blowing at around 10kts so we were having some good runs. Anyway, my Nephew wanted to jump over board while we were sailing so I thought I should take advantage of this and use him as a guinea pig
So, I attached him to the rear aka via a surfboard leash to his PFD. The leash was just the right length so that from where I was in the rear seat of the TI I could easily unleash him if things went bad...
Once we were at cruising speed he dropped off the tramp. and ... our momentum came to a grinding halt. When he was in the water, we were moving forward, but only very slowly. He was comfortable getting slowly dragged and there was no real danger. Admittedly, he did struggle to get back in the boat but then again, he's only a little fella so not much strength in the arms.
My newphew is only 12 years old (maybe 40kgs) and his mass pretty much stopped the kayak. I think if I went overboard, it would stop and I could easily pull myself up the leash and back into the kayak. I will get out for a sail in the ocean with my Brother soon and test the theory."
...and this from Nohuhu P3 here:
viewtopic.php?f=71&t=27286&p=113001 "Well the test results are in,...
I just happened to find myself with a hitchhiker on my tramps this weekend (another story) who weighed about the same as me, so I leashed him up and tossed him overboard
We were on a strong starboard tack into 15-20mph winds (in sheltered water). I tied his left wrist to a 9' quick-release stretch leash and the other end to the right rear Aka, (about a foot from the hull). He "bailed" off the windward side and hit the warm Hawaiian water with minimal splash and hysterics. I remained neutral in the seat and did not assist.
The Good News:
The boat quickly came from about 6 knots to a slow crawl, and turned gradually into the wind. After turning, with a couple kicks he was aboard. Nothing dramatic. It all took less than 30 seconds.
The Bad News:
None really, but I did observe that if you are wearing a VHF radio/sunglasses/hat, you may become preoccupied with saving them and not yourself. Consider the risks here. It will make things harder if your hands are full of any sort of gear (including your precious rod/reel, electronics, etc) that may have washed over without a tether.
Conclusions
1. I am confident that in fair seas, the AI will not go far with you attached to just about any point. (I suspect you will have a harder time contending with whatever caused you to take a dunk in the first place- like high waves, collision with a reef/obstruction or an angry bullshark who doesn't like red Hobies).
2. Use a wrist strap or harness. You would not want to be dragged by your feet for any distance. It will impede your swimming and recovery.
3. Unless you are fighting a record fish, let go of everything else but your lifeline!
4. The boat should slow within a few seconds, but can still pull you along slowly until it turns into the wind. Making yourself "larger" will increase drag and should help to stall and turn it. THIS is your chance to get back onboard before it shoots off in a new direction.
5. A long leash is not necessary. Shorter may be better
The ocean is unpredictable, but after this quick test, I feel confident that a leash will work and is far more likely to save me, than kill me.
I look forward to Maui Bob conducting tests with his TI. With its faster hull and BIG sail, that would be a whole other rodeo ride! (Good luck finding a crash test dummy for that one, Bob)."