If you are sailing in US waterways, how about subscribing to an "air card" like the one offered by Verizon or Kricket; no bigger than a "thumb drive" inserted into a USB port. For about $50 USD per month you'll have unlimited access, just about everywhere you go with your
laptop. It is not a very fast WiFi connection for uploading/downloading very large files, but it is reliable and coverage is available in most places. Mauritz