Better find out for sure just what the range is offshore
. Their satellites antennas are pointed at the USA and were never really meant to extend far past the landmass.
From here: Welcome to WxWorx: Support: Sales FAQ
"How far outside the continental US are the XM WX weather data available?
data is derived from the 145 ground-based sites in the U.S. NEXRAD network, which covers the contiguous United States, and up to approximately 150 miles outside the borders of the 48 States and coastal waters depending on the actual location of the Doppler Radar. The lightning
data covers up to approximately 200 miles outside the borders of the 48 States. Other products when and where available such as winds aloft, fronts, infrared satellite
mosaic, sea temps, wave heights etc. are generally viewable to about 500-800 miles outside of the borders of the 48 States. Coverage is not available in or around Hawaii
. This information should serve as a general guideline with the understanding that while the coverage may well exceed 500-800 miles in some case, depending on antenna
type and placement, we cannot provide specific coverage availability and details for locations outside of the borders of the 48 States other than what we have stated here."
There is a link to an unofficial map of coverage on that page, but it is a dead link.