Not really a big deal, although I don't see 50MP images working underwater. At this point it's really a question of go cheap or go for interchangeable lenses. Go cheap would be the TG-6. ILC would be the E-M1 mk ii which is somewhat the direction I'm leaning.
I have a little Western Digital "My Passport" 250GB SSD that I use for dealing with images/video from drone work. Hehe, you think UW photography is bad, wait til you have 15GB of stills from a drone mapping project. Rinse repeat 4 times for a days work.
My "laptop" is a Microsoft (sub)SurfacePro. It's honestly, bar none, the lousiest laptop I've ever owned in my life. It does however do the job and has some unique features I need for work. No other windows tablet has that form factor and a glove type case that I can use. Anyway, I digress.... the sub-surface has a small SSD so the My Passport is a practical way to deal with that. It also makes ingesting the images and processing them on my desktop much easier. My image library lives on a NAS device anyway with mirrored drives.
The surface works well enough that I sold off my clamshell laptop because I never used it. I've been eyeing the Surface Pro 8 but it hasn't been a priority to upgrade. I currently have a Surface Pro 7 and it has some hardware quirks that caused unsolicited reboots among other "features." It does get points for being rugged. It is not, however an iPad Pro, nor does it have a camera that would do justice to any mobile device made in the last 10 years.