I don't think you can do a lot about the land elevation with a handheld marine band radio.
On my two Standard Horizon HX 890, here in the hill country I can listen to San Antonio NOAA like it was a real person sitting in my garage.
Here I'm high, 800' above San Antonio, the tower is high at SAT 17 miles away.
But from an Arroyo City palapa, there's enough land with coastline bluffs between there and Port Isabel, also happens to be 17 miles away, I barely get any signal from NOAA, unless I'm in a boat on Laguna Madre, and it comes through sharp. Line of sight is everything.
On the bays, we've had no problems with a couple miles and islands between us, and radios mounted just above the water, but those are pretty low elevation islands (this one is the spoil from a channel cut 100 years ago and abandoned for a better cut - great fishy water).
The great things about GPS/DSC result from a hull registration (MMSI) coded in, and specific to the radio and hull, Ships navigating with AIM and pleasure craft navigating with DSC see you on their nav screens (you can poll a list giving their direction and range), the Coast Guard has you in their database, and with All Ships distress call, or even a pan-pan for mechanical failure, everyone can find you on their GPS. And of course this is most valuable for going offshore.
You can have coded private communications as a group, and find each other on GPS (group monitor, group position, and navigate to a group member).
The SH HX890 is the latest and lowest-priced hand-held with these features, but that's still $200.
The SH HX40, is the tiniest simple handheld VHF out there, and with 6W.
Scads of battery on the HX890 (a weekend's worth), but can't vouch for the HX40.
Marine Band is 156 to 162 MHz
Aviation band is 138 to 142 MHz, so there are no overlapping channels and "ham radio" frequency band is between the two.
From what I read, aircraft needs prior clearance from an FCC Administrator to use a marine band public channel, and can use port and intership channels when involved in search and rescue. I know it's illegal to transmit on marine band from land, unless you're a licensed station.
Might be worth asking Donny, paveglass - he spent a career on the aviation rescue side, including tours of duty in Alaska.