Enter the SOLA 500 (500 lumens of power) which is used primarily as a focus light as most things I shoot underwater are really tiny, the 60mm macro lens takes forever to focus.
Here’s a video by Scott Gietler reviewing the SOLA 500..
It took me over 50 minutes to get this shot of the (one-claw) harlequin shrimp (Anilao, Philippines). Had I used a focus light in this shoot, I would probably have 2 or 3 more decent photos as the lens wouldn’t focus on the subject when it was between two rocks. The purpose of a focus light is to make the lens focus faster on the subject.
Same story with this pair of tiger shrimp (Anilao, Philippines) — over 20 minutes and 60++ shots and this was the most decent of the lot due to the shrimp being “malikot” so the lens had a hard time catching up. This tiger shrimp is about 2cm long.
I can’t wait to test this in the water, hopefully soon. Above water, it makes a handy flashlight!