The iPhone is waterproof and you can take a photo with the physical volume up/down key. I've used it underwater a couple of times, none of my other proper cameras would be able to do that. My two cents.
I've used my olympus TG4 underwater at a depth of 15m (best I could do without scuba), and had it trailing on a lanyard on my wrist whilst swimming in the ocean. I'd like to think nobody would subject any current smartphone to these sorts of conditions, and expect them to survive, nor believe the marketing rhetoric.
One other thing I do like about the TG4, nice big buttons, and I've had plenty of opportunities to use it in rather adverse conditions.
"Splash, water, and dust resistance are not permanent conditions and resistance might decrease as a result of normal wear. Liquid damage is not covered under warranty, but you might have rights under consumer law."
I think of it more as good to have for an accidental drop, rather than a specification to rely upon for regular underwater photography, although the more recent phones do reach ever higher Ingress Protection (IP67, IP68 etc) water/splash/dust ratings.
Anecdata but I’ve jumped in saltwater to get ahold of my stupid dog that fell off our dock with my iPhone 12 in my pocket. I am typing this response on said phone :)
Took my 12 mini on a day of kayaking, water got into the lenses and broke the faceID camera. The water in the lens eventually evaporated, but the faceID cam seems permenantly broken.
They are water resistant, but I wouldn't use it in water as a matter of course. Maybe if its in pristine/as new condition, at best - I've dropped mine a few times, which probably didn't help.
