If you're heading to the beach this winter, you might want to pack the Pentax
Optio W20 or the Olympus Stylus 720SW in your beach bag to capture your
As for dedicated underwater modes, Olympus bests Pentax. On the still side, Pentax has a single "Underwater" mode, which simply adds a bluish cast to images without optimizing shooting performance for aquatic conditions. While the Underwater mode might make a shot in a swimming pool more oceanic, we recommend against using the Underwater mode of the Pentax Optio W20 while in the real seas. If the water is exceptionally clear the colors of the sea life will appear much more vivid in Auto White Balance settings. And even if the water is exceptionally clear, as distance from the camera increases, the light refracting properties of the water will naturally add a blue-green tint to your images. We strongly suggest using either Sports mode or Program with Pan Focusing for underwater shooting with the Pentax Optio W20, set to Auto White Balance. If you can get really close to still subjects, consider macro focusing, again on Program, with Auto White Balance.
The Olympus has four still Underwater Modes: Underwater Wide 1, Underwater Wide 2, Underwater Macro, and Underwater Snapshot. Strangely, all but the last mode are described as requiring an underwater housing, although this camera is depth-rated to three meters (10 feet), as is described in the Underwater Snapshot mode. The descriptions of these modes, which appear onscreen after a few seconds of scrolling to one or the next, are a bit strange. Underwater Wide 1 is ideal for "underwater landscapes" (seascapes?), Underwater Wide 2 locks focus ∞ for shutter priority shooting, Underwater Macro is obviously for macro modes, and Underwater Snapshot is for taking photos "at the beach or in the pool." There's no tint, hue or casting applied to the image in any of these modes, and white balancing can be selected manually or automatically in any of these shooting modes. We strongly suggest Auto White Balancing, based on this camera's excellent performance at Auto White Balancing.
With both cameras set to Auto White Balancing, we suggest using the "Auto" button in Adobe Photoshop CS2 and Photoshop Elements Levels or Curves commands to quickly remove the natural blue casting and to replicate the underwater world and it appears to the human eye.