I have seen several solutions used but the one I like best is one I stole from someone else that uses clump foliage from Woodland scenics.

A year or so ago I began playing Cruel Seas by Warlord Games, MTB level naval warfare. To simulate the plumes of water from near misses and torpedo explosions I unwind a paper clip and glue one end to a plastic disc (a half of plastic disc in the case of the torpedo hit, so that I can place it against a model ship).

Next I take some pieces of the Woodland Scenics Clump foliage and glue it to the paper clip using superglue or Cyano Acrylate glue(CA), trying to create a towering column of water. Once this has dried I take cheap CA and working in a well ventilated area drip CA all over the clump foliage to solidify it and bind it all together.

Then I leave it for a bit.

When I come back to it, it has become a solid mass. Next I take it out into the yeard and spray it. Usually a light grey followed by a second spray of white. Usually that is enough but I may give it a light dry brush. Finally I paint the base to match the cloth we use the games.

It's a good technique, I first saw it used for coloured smoke, the supporting wire was left long and the smoke tailed off quite realistically. I have also used it to form the base of a wind elemental reflecting the little whirlwind of debris kicked up around its' 'feet'. It could also be used to simulate air-bursts.

It all depends on colours used blacks and earth colours for ground burst explosions with scatter material - twigs etc glued on the surface of the blast.

We had the ships out for a game tonight so I took a photo to show what I mean.



These were made exactly as described above.