This was originally discussed with Finchaser. He remembers that when people first started kayakking many years ago before it became a "craze", that guys in yaks fishing the ocean or big water would do this as SOP. This way, if you fall, you are never coimpletely separated from the yak.

A few friends of mine who fish big water a lot never go out there without
1. being tethered to their yak
2. having a set of swim fins tied to their legs in case of accident.

Those who yak in big surf a lot may have issues with this, saying the kayak could hit you in a big swell if you became separated from it, but my question to those that disagree would be...."Why do surfers wear leashes?"

In a yak, if you are out in big water at night, deep and swift current, if your yak gets away from you it could be your death that follows.

Wearing a leash/tether has it's own set of considerations, as to length, elasticity (I prefer standard poly rope) and several other factors, best discussed in a separate thread. So if anyone wants more detail, feel free to start one, and we'll try to help.