Loz,
do a search as this topic has been discussed before and you may find your answer there...........try 'water party', 'fiesta del agua' or variations of.
at Es Paradis there is no one cannon as such, just several small jets (5 or 6 i think) that water is comes out of. The main dancefloor is bowl shaped (with steps) and the water comes from near the top of the steps pointing into the middle of the dancefloor.
N.B. The area that gets flooded is only a small proportion of the the club........so if you don't wanna get wet then there'll be plenty of room to dance.