SJ Cam SJ4000 action camera review for scuba diving

The SJCam SJ4000 isn't a new model, it's been around for a few years now, but some of the footage on YouTube suggests it's a bit of a sleeper, and much, much better than the ridiculously low prices they sell for would suggest. So I bought one.
Mine's actually an SJ4000 WiFi, but WiFI isn't important to me, I went for it because a spare battery and stand-alone battery charger were included, things I'd have wanted to buy as extras.
Oh, and if you go for one, make sure it's a genuine SJCam, there are a lot of clones and rip-offs on the market.
First job was to try the housing without the camera, then, using the default Auto settings and shooting full-HD, 1920x1080 video, I took it diving to see how it performed.
Bottom line, it's a cracking little camera; take a look.