Maybe OP means something different. I remember in good old days there was a thing called "asymetrical satellite
data" or sometimes "satellite DSL". It worked like this: you had to send requests by landline/modem/slow cellular and you were receiving data back by satellite
at megabit speeds. I had this installed, I had a "sky" PCI card which was actually a sat tuner, and a dish pointed at one of Astra sats. I believe I paid some reasonable moneys for traffic. The only drawback was a latency - it took some time to "that side" to respond via satellite, but once you had a responce - download was very fast. I believe the system died as cheap broadband
I don't know current
state of affairs in this niche, but there are some options available, google
for "one-way satellite internet".
So, technically speaking OP was using the correct terminology, but I am not sure he was meaning exactly the tech I was talking about. As well, there will be a need of a cellular data channel for upstream traffic anyway, plus I don't even know how to make this thing work
on the boat
with constant motion. You can, however, screw the dish to the dock
in marina and enjoy more or less high speed sat inet.
PS googled this
(pricy, but requires smaller dish) and this
(looks pretty interesting with quite reasonable prices! Most Meds will require 90-100 cm dish to reliably receive data with them)