[Little Ray]

Its called “surface-search radar”. If you're in a bad neighborhood (like Somalia or the Straights of Malacca) you keep a security watch. If someone gets too close, you go to a heightened alert status. If they actually start to approach you, you let ‘em know you're awake and armed. They go look for an easier victim...

If you actally read reports on piracy (they publish ‘em on the net) a lot pirates are stopped by alert crews and high-pressure hoses. Alert crews and autocannons might go a long way toward putting them out of business.

Of course the only way to actually put them out of business is to pursue 'em into their home ports and burn the port down around the ears of the pirates and their supporters. Nobody really seems to have the balls to do that any more.

[1rudeboy]

Zodiacs don't show up on radar. Your only options are either floodlights or as mentioned above, thermal imaging. And again, you have to have one or two people awake and dedicated solely to the task.

The notion that some guy standing on the bridge periodically glancing at the scope is enough is simply not realistic.