Depends on what you mean by on cruise
. You can get 3G/4G pretty much up and down the whole east coast
and most of the west coast
, up to 4-6 miles offshore
with a standard cell phone
. Further out you need a booster.
you can use a long range wifi
and pick up the local Starbucks with having to go in.
Further that this you have to use satellite
(very expensive) or shortwave radio
If you want to read more there are a dozen threads or so that have covered the subject in great detail.