And would the Sealife Mini need a case?
No, it's integrated into the camera.
Waterproof to 130 feet, rubber armored and built to survive drops, the Mini II was an ultra rugged camera and the perfect companion for any outdoor activity.
The Sealife Mini2 has a built in flash - it's above the lens so not the best place for it since flash in line with the focal plane of the camera lens often causes backscatter when the particles in the water reflect the light in the shot. It will also work with their optional SL961 external flash or SL980 video light - both of which also include a tray - the body doubles as a handle. Since the Mini II also has a tripod screw there might be other tray/light options you can find for less money. A good non-dedicated flash will still be more though most likely.
It also shoots Standard Definition video (640x480) - due to it's age, it's not High Definition.
So good for Youtube or showing your friends on your computer but it won't look so good on a big HDTV.
A GoPro 3 Black is already dive friendly.
The HERO3 camera housing is waterproof to 197’/60m and is constructed of polycarbonate and stainless steel for ultimate durability. The HERO3 has a new improved latch closure that offers one hand open-and-close functionality and locking.
The downside is that it's both a fixed focus and a fixed zoom camera. So any close up shots you'll have to get close.
If you set it to photo mode, every time you press the button it will take one. The default setting takes 12MP stills which is pretty good.
It also shoots all sorts of Hi-Definition video in various formats. 1080P/60 is typcical HDTV broadcast quality and it has 2 modes above that.
With burst mode you can even shoot a sequence o shots if the subject is fast moving then pick out the best one later.
In Photo Burst mode your camera takes multiple photos in short time intervals—
3 photos/1 second, 5 photos/1 second, 10 photos/1 second, 10 photos/2 seconds,
30 photos/1 second, 30 photos/2 seconds or 30 photos/3 seconds.
Read your manual, there's also an option where you can shoot video continuously and take a still shot of the same thing by pressing the button.
It
can't however drive a strobe - it's a video camera that does stills not a stills camera.
An option would be to add a video/focus light and leave it on all the time while shooting photos that need more light. You can probably get a cheap one including tray for around $100-$150. It's important to note the beam angle on the light if you do, the GoPro has a 170
o field of view so you want a light(s) to match that as close as possible. Otherwise all your photos will have dark rings around them since typical dive lights are in the 7-15
o range. Two lights is best - aimed to provide overlapping coverage.