Cell phones for UW shooting is in state of flux. While the latest crop of Samsung, Apple and Pixel phones produce great images above water using them UW even in the best of housing choices (Kraken, Watershot plus another brand I can't recall) introduce challenges.
Most require an App installed then protocols for start up, changing settings, etc. Battery life is usually challenged too.
No one uses external flash as you can't synch your phone's flash plus this would suck your phone's battery even faster. A fixed LED video light up to 3000 lumens is the most commonly used choice.
I am an ardent advocate for compact cameras especially the latest 1" models from Sony and Canon for UW shooting (Full disclosure I'm a Fantasea and Ikelite dealer PLUS actual user of both brands for years.)
Ease of travel with lower cost, size and great capability make these winners. Compact cameras like my Canon G7X II in a Fantasea housing with Inon strobes is all I've used for 3 years after decades of hauling SLRs around the world. It's been wonderful
I'm seeing less and less people bring a SLR or mirrorless ILC (Interchangeable lens) camera o my trips these days too. For example I'm taking 25 people to La Paz Baja next week. Two have full sized SLR housings and 14 have a compact camera with maybe one small strobe.
That said my iPhone Xr and next generation camera phones will be where I think the market eventually goes.
There are now printing services on all manner of materials including aluminum and coffee table trip memory books that look great with DECENT exposed and focused cell phone or compact camera pictures. Printing has evolved rapidly with lower cost and better quality each year.
This will also continue to improve with technology including AI and Apps in cell phones and compact cameras too.
I haven't housed my iPhone YET but truly believe this as the norm is coming. For UW photography and travel imaging in general it'll be more popular than people snapping up GoPros which has waned a bit. They're still great for video but for stills a good 1" sensor compact has it beat, NOW.....
Just one old guy's opinion after diving for 50 in 2020!
David Haas
Haas Photography Inc.