Dish doesn't actually do sat internet, they just partner with Exede or
Hughes.
Both Exede and Hughes use spot-beamed
service for their primary offerings. I think Exede is only spot-beam while Hughes still has their older Ku based wide footprint sat
service which is only available through resellers.
The spot beam service won't work for cruising as it requires central office (NOC) changes any time it's moved more than a few miles. Assuming you could aim the dish properly in the first place, which generally takes a trained technician for those Ka band units.
As the previous poster said, there are sat internet options for mobile customers, but they're much more expensive.