Updated on August 13, 2026. Onboard, 4G/5G and Starlink do not serve exactly the same purpose. The mobile network is often the first link to use when available. Starlink provides an alternative access method, with its own hardware, plan, power and sky visibility constraints.
The short answer
For coastal sailing, start by checking operator coverage in your usual area and testing actual reception at the harbor and at anchor. A marine dual-SIM router, a suitable cellular antenna and a properly installed Wi-Fi network may be enough. Add Starlink if your usage requires greater continuity, throughput or connectivity outside mobile-covered areas. For offshore sailing, check the Starlink plan conditions applicable to the ocean and keep an independent safety communication method.
Why there is no guaranteed 4G range from the coast
Useful range depends on the position of ground antennas, their orientation, terrain, the height of the boat’s antenna, sea state, congestion and the frequency bands used. A single value in nautical miles would therefore be misleading. The Arcep publishes mobile coverage maps and measurements and recommends its "Mon réseau mobile" tool to compare operators. These maps are a starting point, not a promise of reception at sea.
What a marine router must actually deliver
- One or two SIMs: two operators can reduce the risk of a common dead zone, without guaranteeing coverage.
- An Ethernet WAN input: it allows using Starlink or the marina Wi-Fi as another Internet source.
- A true failover strategy: having multiple links is not enough; the router must detect loss of access and switch to an available connection.
- Consistent antennas: number of MIMO streams, cables, connectors and mounting must match the modem. A cable that is too long or unsuitable can negate the benefit of a good antenna.
- Marine-grade power and installation: protections, cable gauges, ventilation and waterproofing must be planned according to the product.
Technical datasheets for Peplink, for example the BR Pro family, let you verify modem, bands, antennas, power and interfaces. You must check the exact model and its radio region before ordering.
What Starlink changes
Starlink does not depend on a coastal mobile antenna, but it requires a sufficiently clear view of the sky, continuous power and a plan that allows the intended use. Conditions differ at the harbor, in coastal waters and offshore. Starlink currently states that some Roam plans cover coastal waters up to 12 nautical miles with time limits, and that an ocean mode or a suitable plan is required beyond that. These rules change: always check Starlink’s ocean usage help page before departure.
Recommended architecture by scenario
| Program | Architecture to consider | Checkpoint |
|---|---|---|
| Home harbor and usual anchorages | 4G/5G router, one or two SIMs, onboard Wi-Fi | Actual operator coverage and data allowance |
| Regular coastal cruising | 4G/5G as primary, Starlink as secondary link if needed | Failover, power, sky visibility and plan |
| Remote work onboard | Two independent links and failover policy | Critical apps, quota, network security |
| Offshore | Starlink for Internet, dedicated satellite communication and separate distress | Ocean plan, power budget, redundancy and emergency procedure |
Mistakes to avoid
- buying an antenna without checking bands, connector count and modem compatibility;
- confusing the presence of a signal with a connection stable enough for professional use;
- choosing a plan based on an old tariff or plan name;
- relying on Starlink as a distress means;
- installing a system without measuring its power draw in the vessel’s energy budget.
Before choosing
List your sailing areas, the number of users, priority applications, data allowance, vessel power budget and space available for antennas. Skysat can then verify the router, antennas, failover to Starlink and required protections, without promising coverage that neither the mobile operator nor the hardware can guarantee.
Main sources: Arcep, mobile coverage ; Starlink, ocean usage ; Peplink, BR Pro Family Datasheet.
