As a tactic, fire hoses may be quite useful in actually "repelling" the boarders. That is, preventing them from boarding or staying aboard the ship.
The strategy in handling such pirates, however, should be to end their pirate days by killing them all and making sure that it gets plenty of publicity.
I haven't seen anything in the articles suggesting that these guys are doing anything today other than preparing to attack some other ship. That's not good enough.