5. Power is very important, but size and particularly weight in water must be considered before purchasing that new Super Nova 9000 Dual Overhead Cam Posi-traction Plutonium Powered strobe your buddy bought. More powerful strobes are physically larger, and when poorly designed, can be negatively buoyant. Perched on the end of long strobe arms (essential for wide angle work), heavy strobes, with their weight amplified by the leverage of the long arms, will become impossible to hold. Neutral buoyancy in the water is essential. Finally, strobe power is often referred to by the measure of "Watt Seconds". These aren't Jim's throw away slides, but rather a measure of energy capacity of the strobe -- a 200 watt second strobe for instance. But this rating is no way to compare maximum illumination, as strobe reflector efficiency and beam angle will affect the maximum illumination as well.

6. Almost all modern strobes allow the option of both TTL and some form of manual operation. As TTL works far less reliably in wide angle underwater photography, a strobe with an intelligent selection of manual power settings is desirable. There will be many instances where manual strobe control is the only reliable way to correctly expose a shot. These manual power settings ideally will cover a multiple
f stop range, in small increments. Strobes with 2-stop increments (Full, 1/4, 1/16) are less desirable, as these settings represent HUGE single changes in illumination per increment, and thus do not provide a fine "bracketing" control. Strobes with Full, 1/2, 1/4, 1/8 are better, as these represent 1-stop increments. This is still too large a change, but very likely the best you'll find. Therefore, employing a 1/2 stop diffuser will allow the photographer to achieve the intermediate settings and the subtlety of control desired. The strobes can now be fine tuned and bracketed precisely, to achieve the perfect amount of fill light to balance with the ambient light.

7. Fast recycle time is very desirable, but don't be fooled by unrealistic claims. Accuracy of recycle times as indicated by the ready light for peak strobe output can be quickly tested with a digital flash meter, and many strobes are off by up to a full stop (or more!) when fired immediately as the ready light comes on. Waiting excessively long for the strobe to fully recycle may cause you to miss important shots. That manta ray is unlikely to pose above the sea fan forever, and you'll want to shoot as many shots as you can before it swims off.

 8. Warmer color temperature. Many will prefer a slightly warmer color temperature strobe for wide angle work, as generally the working distance is greater than with close-up photography. The water will increasingly absorb the longer 'warmer' wave lengths the farther away your strobe is from the subject. The lower the color temperature of the strobe (measured in degrees Kelvin) the warmer (redder) the quality of the light. A 6000 degree K strobe will produce a cooler "bluish" quality light. A 4200 degree K strobe will produce a warm reddish-orange quality light.