The (Gold) Fish is from my 10 gallon aquarium and the Clown (Mask) was captured at the London Children's Museum. (London, Ontario, Canada that is.) With Photo Shop I first created a black background layer, then mashed around the "Clown" ceramic mask, copy and pasting it over the black background image. Next I did the same for the Fish, pasting between the background and clown layer. If you can see the bubbles, they were created by making a circular marquee mask then adding a faint outer glow in the layer properties. Using an eraser brush on each layer to soften the edges, the using photoshops lighting effects (directional) to get some continuity and depth to the collage. Here's how I got such a sharp image of the fish without the use of an underwater camera case, and without glare from particles in the water and or the reflective surface of the glass:
With the camera mounted on a tripos only a few centimeters away from the surface of the glass, I attached a Canon Speedlite 420EX external flash to my Canon G2 Powershot camera. I then angled the flash almost straight up wards, and held a piece of white paper about six inches above the top of the uncovered aquarium. Setting the camera to macro mode with an apeture of 8.0 and ISO setting of 50, shutter speed 125 of a sec, I indicated to the fish that I wanted him to approach the lens. (I always tap on the glass of the aquarium before feeding time, this gets the fish to follow your finger, as I usually trace it along the glass until I make a path to the top of that tank, and this is where I insert the food. After a couple weeks the fish always respond to the finger chase / food game). When the Gold fish was in the right position, I used a remote control to release the shutter. With the flash bouncing down into the tank from above, none of the particles in the water reflect back towards the lens, any reflection would be up towards the direction of the bounced light. This also prevented the scales of the fish from bouncing light and glare back to the lens. That's about it.Cheers!