While I appreciate that getting GPS from a phone will work for a lot of people, it doesn't work for me for the vast majority of my diving.
Most of my dives are shore dives and as I swim out from the entry point, even using the phone to get the spot I jumped in won't be accurate to where I descended, especially with long surface swims.
On my last 3 liveaboard trips, they used tenders to get from the main vessel to the dive sites. Sometimes we'd go more than a kilometre. The tenders were small and crowded and I wouldn't have been happy taking my phone (even in a dry bag) on them.
Interestingly, I have been recording my dive entry points for 15 years and my exit points for over 5 years. By "entry point" I mean the location I left the surface and "exit point" I mean the location I surfaced.
When I first started doing this, for shore dives I would use Google Maps to get an approximate location. For boat dives I had a GPS logger/ When doing dives off a tender, I'd put the GPS logger in a ziplock bag and the tender driver would keep it in his pocket. For a while, I had a (somewhat) waterproof Garmin running watch that I could either attach to the boat somewhere or get the tender driver to wear it. This worked well, but required a bit of manual effort.
For the last 3.5 years I have been using a Garmin Descent Mk1. This works great for all my dives. It is particularly good for the entry point as there's plenty of time to pick up the satellites but not so good on the exit as Garmin don't turn the GPS on until the last second. Exit location can be as much as 50m away - not great to show a car park as the exit point on a shore dive.
Having GPS in the dive device itself provides a much better and easier way to record entry and exit locations.
I know at some point my Garmin will die. If it can't be repaired, I'm not sure I want to get another Garmin. While the Mk1 has been "good", it could have been "great" if Garmin had the slightest clue as to what they are doing.