Water cannons need water, which is an annoying and limiting logistical consideration. Tear gas can be blown back into friendlies.

Sonic cannons need...power. Presumeably not so much that it becomes infeasible.

And .50 cal weapons, while fun, are military grade weapons not necessarily appropriate for civilian craft.

-Siege

You prefer permanent hearing loss over temporary pain?

According to the graph on the BBC news article, the intensity of the sound generated by the LRAD at full power is less than 120dB when you're over 20 meters away, dropping under 110dB when you get to 100 meters. Judging from personal experiences at such noise levels, yeah, I'd definitely take that over puking, coughing my lungs out and feeling like someone whacked me in the face with a bat.

Right next to the device, though, at 150dB, you could start missing CS.

What kind of skill would it take to land, and stick, a CS cansister into a boat at 200m? I'm thinking that the LRAD, with a continuous beam with a 9º field, is likely easier to aim than an arcing lobb shot. You'd have to lead a moving target because of the speed of sound, but still that beats trying to lead the target for the canister. Sure you have to keep the LRAD trained on them, but that is another benifit of the LRAD. You stop the immediate effect at will. A CS canister has no such option.

Also i think they have a quote in that news article to do with using the LRAD to "determine intention"? That might imply they might have something a bit nastier onboard. While likely not a cauldern of hot pitch waiting to be dumped on top of someone attempting to board, it could be something more dangerous that they would argue was appropriate to be used against attackers that pushed past the LRAD.

Indeed i expect having the equivalent of my first wife squawking at me, while not enjoyable, is probably preferable to having a gas canister tossed on me. Especially if i happened to be some lost dumbass in a wooden boat that wandered too close to a US Navy boat. While the chance of a healthy individual dieing from the CS canister is quite low, there is the small matter of the physical landing of a canister launched at high enough speed to make it a couple hundred meters. Also if i was indeed some lost dumbass it's entirely possible i, or my passensgers, are not in optimum health.

However i think the biggest reason for the US Navy to use LRAD is the political implication of a US Navy vessle being outfitted and using a gaseous chemical weapon, "lethal" or not. Especially when the intended use implies a real possibily of it being used against civilians.

Based on the CNN review, the LRAD also serves as a computer-generated bullhorn with a long selection of phrases in a variety of languages.

The user scrolls through a PDA-like device, clicks on the phrase desired and then selects the language option.

So yes, one can send messages at range with the bullhorn.

-Siege

After the 60's americans have a real image problem with fire hoses being used on crowds and tear gas cannot be controled once fired and can drift god knows where.

They should use the sound amplifying weapons from "Dune". Those have excellent range and are variable (killing shots, paralyzing shots, skin flailing shots, etc...)