A business / consumer wireless network generally does not extend beyond 25 meters and that assumes no walls blocking the signal. A telecomm's (AT&T, Sprint, Verizon) cell tower in general has a range of 1 to 5 miles. That depends on the terrain, wattage, and the exact specs of the equipment used. Under the best conditions if Verizon were to put a cell tower at the edge of the shore (a really, really, really stupid idea to say the very least), then you can potentially receive a signal 5 miles away from land.
You, my friend, are going to need a remote satellite internet connection. Sounds expensive? Well, that's because it is...http://www.groundcontrol.com/maritime_satellite_internet.htm