: It's hard to believe no one has captured a rolling kayak with an underwater
: camera. What are the limiting factors - low light, water clarity... ?

Those are the two biggies. The kayaker and allthe action is in shadow, so you need to supply a rather large amount of fill light over a rather large area.

Look for a location with a very reflective bottom (white sand would be nice) and a depth of 6 to 10 feet. Failing that, you'll get beter light quality for the dollar from a reflector. Depending on how may assistants and dollars you have, you might choose to use a highly reflective white or silver fabric, (polyester, millium, etc.) or weighted panels of plywood, masonite, or plastic which have been painted white. You will probably want a reflector 20 feet long or longer, which is why a convenient beach was the first choice. The reflector can be made, mounted, and adjusted in sections. You want to keep the reflectors out of the image area, but they are most effective the closer they are to the subject.

The time of day influences the amount of light that penetrates the surface of the water. You probably want to shoot close to astronomical noon -- maybe give or take 90 minutes. While light will be coming from nearly directly above, which is not too photogenic for topside pix, the reflections from the supplmentary reflector(s) can be arranged to pour light onto the paddler and the entire length of their boat.

If you need to use the reflections from a shallow bottom, you may have to wait for the sun to reach a certain altitude to give the best lighting. The best time can be difficult to forecast in advance, but researching this is a pleasant experience. About 10 am take up a position on the shore with an umbrella for shade, a cooler filled with ice, and a large pitcher of margaritas, or other cool beverages. Each 20 minutes wade into the water and snap a picture of an anchored kayak (upright or inverted) and return to shore to consume a portion of the pitcher. After 4 hours, or when the pitcher can no longer be refilled, you should have 12 pictures on your disposable underwater camera. have them developed and select the best one. The next day go back with a new disposable camera, a refilled cooler and pitcher and wait on shore until it is time to get your pictures.

there may be some regional speech impediments, so be sure you read this correctly: That is 12 PICTURES to a roll of film, not 12 PITCHERS. If you try to consume 12 PITCHERS there is a strong likelihood that the PICTURES will be fuzzy, regardless of the water clarity.

Hope this helps.

PGJ

The advantage of using reflectors is that you can tilt them to capture the apparent angle of the light and reflect it onto your subject.