How about a light that complements your GoPro Hero 3 or 3+ and is waterproof up to 40m? Check out the GoPro In The Dark – Knog qudos Action from Knog.
Knog (bike lights) have produced the qudos action for exactly this purpose.
Waterproof up to 40m depth (IP68)
3 mode settings
Built for GoPro but conversion mounts available to use with other cameras.
RRP is $119.95 (US Dollars)