How far does cell phone coverage extend into the Atlantic Ocean?

Cellular communication relies on land-based towers to transmit signals, so as soon as you move a significant distance offshore, you will likely go out of range. Depending on the service provider's capabilities and their tower locations, cell phone coverage over water may range from just a few hundred meters to a few kilometers from the coast. Beyond that, you cannot depend on cellular connectivity while out on the open seas. Instead, for reliable voice and data communication at significant distances from land, ships and offshore facilities often use alternative long-range communication systems such as satellite phones, marine VHF radios, HF radio, or specialized marine communication networks like GSM-R and FleetNet.