Yeah. 15 at best on a typical power boat with the antenna on a t top, flybridge or pilot house. Blow boaters generally do better because they can put them on top of their mast. Coast guard station towers are usually pretty high up so you might be able to reach them at 30 or so miles out if you're near one.
But, yeah, it's line of sight and transmit power. I laugh at the Nautilus, because you're right, the average boat probably can transmit 7-10 miles, assuming the radio even works
, now imagine a tiny antenna with a person bobbing in the waves. A whole lot of limitations on those units.