It is the flash which has frozen the water streaming off the swimmer's arm.
I have published this picture a few times but it is now hidden in archives.
An intermittent blog featuring photography and pieces of writing all opinions my own unless stated.
The shutter speed dial from my old Nikon FE. In the Auto position the camera is in aperture priority mode. It is up to the photographer to select apertures the cameras set the shutter speed for what it thinks will be correct exposure.

Divide the P5000 by 100 and you have Nikon's latest pocket marvel the P50. It has a 28mm (35mm equivalent) wide angle lens, AA batteries so is truly go-anywhere, optical viewfinder, manual mode, Iso 64-2000, 8.2 Mega Pixels and vibration reduction (VR). So pretty much everything needed on a compact.
Taken by Keith Valentine at last year's World Mountain Biking championships in Fort William. I hope he's not going to charge me for this bit of free publicity for his website at: