Years ago, I was lucky enough to see large Brown Trout swim with their Dorsal fins above the water, to measure strength and size. The Circle dance. This I have never forgotten. One day I was lucky enough to experience this again, this time with the camera under water. The chance of getting this spawning behaviors filmed in still water, no wind, swimming in and out of the morning sun, is close to zero. So enjoy this view.
This is a modification I made for my GoPro Hero3+ Black to make the GoPro sutable for underwater use on a pole or a tripod. I drilled a hole in GoPro housing where the HDMI connector is. Glued a milled aluminium tube to the housing, and made a plug with o-rings of the HDMI connector. Video out and power in. And now the GoPro is usable for underwater tripod or polecam recordings.