proper water plooms in films are not done using HE.
theyre done with a air canon..........
Depends on the productions requirements, and the proximity of the crew/cast. The water hits in the Thames boat chase for The World is Not Enough were Nonel initiated HE.
I have a quantity of surplus endecotts sieves, both 4 inch and 6 inch diameter in various mesh sizes which are surplus to my requirements. PM me if you are interested,