"Jack Dale" wrote
I remember Practical Sailor testing both knives and tethers by
recording how quickly a tether could slashed.

Also, I believe that when one of tall ships went down a crew member
could not get free of his tether and was dragged down.

Since then, snap shackles seem to be the favoured attachment method at
the harness.

Does anyone have any experience with or knowledge of the efficacy of
the snap shackles? Can they be released under load?

Tack shops and farm supply stores have quick release shackles that work
reliably under load. (Don't ask .... They have a sliding sleeve and a
hinged hook sort of like a pelican snap on a lifeline gate but more
substantial and easier to work.