So based on the feedback there are 3 options I see.

1. Nothing. Hope you can hold on to a line or swim, but you won’t break your back. You could easily dislocate your shoulder.
2. A short tether that keeps you so close to the boat that you can pull yourself back on if you fall off. It would need to have a good quick release.
3. A long tether that pays out so you have a second to “get ready to water ski.” It would need to have a good quick release.