How can you get background pitch black like this?

[dennybeall]

Doesn't say it's a meet. Could just be set-up with most lights off in the building and shoot with the flashes.

 

[Bubba2]

That is an interesting photograph. I was a school newspaper/yearbook photographer while I was in high school and took many pictures of swimmers, divers, and water polo games. I am wondering how the photographer got the relatively still water in the foreground to not be a distracting mess. The strobe is going to illuminate the water in the foreground, plus any overhead lights will reflect from the water. I didn't have an underwater case for my camera or strobe, and shooting at that low of an angle, below the pool deck, would have put my pucker factor up to around 12. Of course, I was shooting with equipment possibly 45 to 50 years older than the equipment used for this photograph. My strobe would have been a half-dead Honeywell Strobanar "club" and the camera would have been a TLR filled with Tri-X that would have been pushed to about ASA 1600 or more. Yes, it was a grainy, but the bigger medium format negatives helped. In those days, people were used to seeing grainy Tri-X pictures from 35mm negatives. My other camera was a 4x5 Crown Graphic and the negatives were enlarged using a cold cathode back on the camera, hence there was not much visible grain, even when pushing Tri-X to ASA 3200. The Crown Graphic with Plus X was great, every eyelash hair and every pore was visible in the print.

 

[photo1x1.com]

Great advice here. To add another thought: grids help direct the light even more. They are available for almost every light shaper.
Shooting this scene outdoor at night in a 50m pool (with a light to help focussing) would probably be the easiest way to darken the background as much as possible before going into photoshop.