There is as you may be aware a healthy guns vs no guns debate going on in the 'to be armed when cruising' thread anyway....
To start anew another thread looking at good alternatives is a great idea.
I have already presented some options over there( Ones I have heard of and researched, I have no first hand experience on this) , so apologies for some repeat posting but I figure that there will be some who may wish not to go through that thread and all it's sordid controversy and heated discussion.
1) As has been suggested Buddy boating. Avoid VHF
chatter however that may give away location and activity. Potential 'Pirates' may be monitoring. Keep on the HF.
2) Toy Guns. Plastic AK47's from Toys R Us look pretty convincing from a distance. The apporaching slightly hesitant would-be pirate may be fooled enough to not take the risk.
3)Piracy at night is common. Keep good watches, dim Nav lights
and avoid any unidentified vessels in suspect areas. Have a very bright spotlight handy, directed in the eyes of an approaching vessel it can make boarding or aiming very difficult. Followed by a shot from the flare gun it might have some results.
4)Piracy or theft at anchor
is probably most common. Remember that even a modest yacht to alot of people in this world screams of oppulence. Keep cash and jewellery out of sight when visiting villages, place noisy pans, or marbles etc on deck as your early warning system of your vessel being boarded. Tapes of barking dogs have been used by cruisers as well.
I guess the best thing to do is to have a plan of some kind. Piracy is very uncommon. Attacks are often by poor fisherman, not modern day Blackbeard types, so deterrants can be very effective. The professional Pirate is generally not interested in your average cruising yacht, Larger cargo vessels are their focus.