Many years ago I acquired a crossbow for cruising - British make , A Barnett - an early model fairly simple with a pistolgrip or shoulder stock - 100 lb pull - which was difficult to load. Once loaded it could fire a mean bolt ( which could take different heads varying from a simple tip to an expanding tri-section arrow, which on initial impact would expand to cause a wider area of damage; ie a bigger wound.) The modern Barnett is a very different weapon see Website
In visualizing the defensive use of the cross bow - I could see an advantage that at the time it did not appear to be illegal to have on a cruising boat. It certainly had enough power to fire a lethal projectile. BUT the inability to reload quickly made it a nonstarter as a good defensive weapon.
If it was a three hundred years ago - the trained English Bowman with his long bow could get off
an arrow every 3 seconds with a good range see: :Long Bow
Unfortunately the long bow was around 6 ft long which means today using it from a defensive position on the average sized yacht would be difficult.
Today many countries regard Bows, Crossbows and Spearguns as potentially dangerous weapons and legislate for their possession and use. Therefore when cruising a check with the intended country's authorities is recommended.
Most Cruisers today have decided against
firearms - for many good reasons - a search of our topics on the subject is rewarding.
As a defensive firearm on a yacht the stainless/steel short barrel Winchester pump action shotgun was voted the gun for the job.