(aka double tether)
Spinlock Performance Safety Tether - Hitch Loop, 2 Custom Clips, Stretch Safety Line (2 m)

This stretchable safety tether has a loop at one end which you attach to your harness via a girth hitch (cow hitch), a short (1 m) leg with a custom carabiner safety clip for attaching to an anchor point or jack line on the boat, and a long (2 m) stretchable second leg with a second custom carabiner safety clip.
Extended length of the stretchable leg is 6-1/2 ft (2 meters).
The two leg design allows you to always maintain one point of attachment for increased safety.