It's made by Benchmark - I purchased mine on ebay but they're available all over the place. They are very popular with hang glider pilots and climbers. David Strickland (S.C.) showed them to me about 6 months ago. You can attach the sheath to your life vest but it works really well on the big side strap on most trapeze harnesses.

Note: the black colored stainless hook will rust on the black coated part (not the blade part) - if you're sailing in salt water, try the all stainless one.

And Oh yeah...they're only about $30; less than a good diving knife.