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.