4G and 5G are going to depend on the mobile carrier. In the US, at least, that's usually going to be somewhere between 850MHz and 2100MHz. I recall reading something more recent about 700MHz being opened up in some areas.
Looks like Germany is 700-2600MHz for 4G, with 5G up at 3500MHz[0].
For underwater stuff it looks like you need something much lower in the kHz range[1], at least for distances of up to a couple hundred feet. Obviously this particular situation involves a much shorter distance. The page on MF radio[2] does mention water, and talks about frequencies up to 3MHz, but that's still way lower than any LTE bands used.
Verizon has used 700MHz for a long time, its their primary band. T-mobile uses 700MHz and 600MHz in many areas (generally as range extension, not a primary band).
so that's Bluetooth and wi-fi ruled out.
GPS is a lower frequency, ~1.5GHz I think, and GPS is already an extremely low power signal.
I don't know about 4g or 5g though.