I have the same drone and I get the distance that is advertised. I have been almost a mile away and still had signal but decided that was far enough and turned around. No upgrades. Make sure you are not still on beginner mode.
I'm not for sure but I would think he was a little too close to shore. A big boat like that puts off a big wake. With that said, I wouldn't have hung around long. It's too bad even with 1600 horses he was still stuck