Reddit mentions of Sony MPK-URX100A Underwater Housing - Black

So looking up the Canon D20 it looks like it is just a base waterproof point-n-shoot in the $200-300 range. If you want better video and want to stay in the same price range then a GoPro 7 would be an option. You do have various other waterproof still point and shoots that you can get waterproof housings to extend their depth ranges that would bring you up to the $500-800 range. Personal I have a Sony RX100v that just the camera alone is $900 though I'm now getting into have some play when it comes to manual settings and can shoot in RAW. You will see a big improvement in quality though to maximize it you need to start bringing your own light whether in strobes for stills and video light for, well, video. Also you will need to look at wet lens for these prosumer level. Just the camera in housing alone won't get you those great whole wreck/reef shots. I'll break down how much my current setup costs with the RX100v, this will be a guide for you since you can always get different products or used to get some of your cost down...or up.

• RX100v $898
  
• Sony MPK-URX100A Underwater Housing $295
  
• Sola Video Pro 3800 $699
  
• Sea & Sea YS-03 Strobe Head $299 x2
  
• Kraken KRL-01 67mm Wide Wet Lens $765
  
• INON UCL-165M67 Close-up Lens $197
  
• Arms, ball clamps, fiber optic cables to trigger your strobes, tray, silica packs, extra batteries, etc
  
  So with this you're in the $3500-4000 range and this isn't even to the DSLR/Mirrorless levels. I don't want to discourage you at all, I love my setup and for the most part it packs small though it is pretty bulky underwater and creates drag though I love the shots that I can get and the video is pretty good too.