I know some commercial fishermen in California and noticed they like to post on social media while at sea. I asked and it turns out they for the most part can get LTE coverage a good distance offshore, to the point that while dragging nets in water 10,000 ft deep they still can use their phone. The cell signals travel much further over water compared to over land.

I will ask one of them for an idea of how far they get when they lose coverage and edit when I hear back. He is on the boat now.