Good videocams for use in self-observation

I’d like to buy a waterproof videocam to “see” my technique. GoPro used to be the one that every other mtn biker used, but it’s been a long time since they were introduced. Which brands and models have you guys tried and what do you like or dislike about each? Mount on head or on the ski? 

I’d like to keep the price under $500 USD.

If the goal is to see your technique I'd stay with a cheap gopro knock off for under $100 with a waterproof housing. They work quite well. Get a suction cup mount (the "gecko" one is really good), this way you can easily mount the camera in the front or the rear and experiment with placement to see your technique from different angles.

If your goal is to record a full DW then the mount and mast is what will make the biggest difference. The next thing is the run-time... My DWs end up being an hour and a half or longer and the only way the camera makes it from beginning to end is by setting it to 1080p resolution, so any money spent on "4K" is wasted... Of course you can use a wireless remote and press the button when you feel like the next wave is going to be awesome and then pray it actually turned the video on (good luck with that)...

The purpose is just to aid in improving my technique. I have an old Pentax waterproof camera that I’ll try mounting in the front of the footwell, just because, well, because I already have it. Will also look at what action cams are available now. The suction cup sounds like a useful thing to have, too.

At this point, you can get a 'renewed' hero 6 on Amazon for about $170.  I have been using one of these for a few years for the exact same purpose and it does great.  Video quality can go up to 4k (but to save on storage and because I am only looking at it through a browser 1080 is more than enough) and gopro's stabilization works really well.  Stabilization, size, and not needing a separate water housing are the keys to me.  It is also easy to find mounts for the gopro.  I picked up a Ram suction mount which came with a bungee tether that I connect to my deck bungees with a carabiner.  Generally don't worry about a mast since the video is just for my own learning.