Mid air collision of drops splashing down. I guess the drop was going up from the spout and it hit slightly off centre so half of it pushed upward.
2 Vivitar flashes behind the splash, frosted perspex diffuser, 'carnival glass' gel on one flash (piece of 1920's iridised carnival glass!)
Triggered with manual push button trigger wired into pc-sync hot shoe's.
Info on creating the splashes : drippy2009.blogspot.com