I used water splash brushes that i downloaded long time ago... see SBS
What is the Water Elemental? Please check my WIP section (SBS) to find out more about that creature.
Techniques I've been used are matte painting inside Photoshop, clipping masks, brush with custom brushes (links), puppet warp, also brush inside SAI, and finally adjustments layers with some filters (blur, motion blur, gaussian blur) back into Photoshop.
Hope you like my creation, lots of great entries, I'm afraid I'm no match with the others.
(•̪ . •̪) ~ Thanks!
Edit: link has been updated.
I decided to put this guy somewhere more dynamic and colorful! Hope you like it :)