These are quotes from a Sailing Gear article.
“Some offshore races are now requiring knives on deck and worn by each crewmember”
“The requirement of a cockpit knife has always existed for most offshore and inshore races sailed under the ISAF Special Regulations. Regulations usually require a knife to be kept in the boat’s safety grab bag as well. These rules mandate the on-deck knife be accessible, secure in its scabbard, and made of a quality steel alloy that can withstand environmental abuse. In 2011, however, several studies conducted following two high-profile accidents each recommended all sailors carry a personal knife.
Consequently, the 2012 Mackinac [Race] Safety Requirements (MSR), used for the Chicago-Mac and Bayview-Mac races now require every crewmember to carry a knife while on deck, and always readily available (i.e., on the outside of your gear or PFD).”
I do have knives on me when aboard and when hunting. My favorite sheath knife is my Dad’s USN knife but I just don’t take it on the boat. When I finish my project boat I will bring it on board after the Christening.
Sheath knives are illegal on merchant ships way back when.