How deep do you dive ?
Assuming you're a certified open water diver, max of 18m.
I doubt those devices are good at more than 10 meters.
Shooting at below 15meters will be very dark though.

I've used the first one on a mirrorless & it's no good at all. It moves inside & since my lens have zoom, it might spoil it & the photo that comes out may be blocked at certain part. I think you'll be better off with those hard plastic cover (like gopro's).

Well, if you're gonna use occasionally then it's ok. And perhaps its a better fit for your type of camera than mine.

Yeah & your lens is a zoom so it moves so you gotta have certain gap when it's retracted. Hence, there's loose space in front of the lens & that's why the position of the camera in the jacket will move. That's why if you can find those GoPro like waterproof hard plastic covering is better.

TS no intention to get dslr with actual waterproofing case?

What about getting a SJ4000 kit??
It is a china's gopro clone
Come with waterpoof case