The use of fire hoses to deter pirate attacks gets a lot unwarranted criticism.
Eagle Speak has an article Arming Merchants here. Commenter Tom recalls the ordeal (here) of the crew of the tug Svitzer Korsakov and says: stop advising sailors to “put up a fight with fire hoses and boxing gloves.”
In the context of the tug Svitzer Korsakov that comment makes sense and expresses the frustration of crews on slower vessels that must transit the Gulf of Aden.
There is no questions that firehoses alone are not sufficient in all cases to prevent or deter attacks. Does it make sense for a 8 kt tug to have to rely on fire hoses alone? Clearly not. On the other hand I think it is prudent for a container ship capable sustaining 24 kts to rig hoses as a deterrent against attacks. From this article at Eagle Speak:
The average service speed of the 10 vessels that were fired upon but not boarded was 15 knots. The average service speed of the 11 vessels that were successfully boarded by pirates was 14 knots.
Container ships have not been attacked even though they "represent about 38% of the traffic through the Gulf of Aden" (Eagle Speak here)
In some cases increasing speed, zig-zag maneuvers and fire hoses have been successfully used to discourage attackers. The value of these techniques should not be discounted in all cases.
Obviously what is appropriate for one ship may not be for another. The same commenter Tom says it himself:
My response: Who’s saying a professional security team is the right response for every ship type?