Saudi led hegemony in Yemen

Saudi hegemony in Yemen is based on the billion dollar military equipment the US sold to it.
Yet despite all the high tech military furnishings, this happens:

http://www.aljazeera.com/news/2017/07/houthis-claim-attack-uae-ship-yemen-west-coast-170729184615831.html

The critical question is:

What more can the Houthis do 

to the Saudis and friends?