I used to own the base 560 which Wandril now does & I had 2 waterproof leather straps. One OEM from Panerai used to be under the description calf cashmere gold strap. My favourite OEM strap which I used many times swimming. It did age over a period of time though.
The other was Kodiak strap bought from the US. Much stiffer than OEM but great for water use & didn’t age.
Believe Di Stefano (spelling unsure) used to make a few as well.
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