If you are docked in the marina you can use the free wifi signal of the marina, dropping anchor a few miles of the coast marine electronics switch to 4G/5G, go any further and the only thing left to use is VSAT. However this will change with the rise of the Starlink network.
Vsat is short for very-small-aperture terminal. Satellites have been placed into geostationary orbit (GEO) and redirect signals to hub stations on the ground which are connected to the internet. A reasonable V-Sat connection at sea might be 5-20Mbps.
Vsat system onboard consists of a dish antenna, often concealed into a awful big ugly dome, ensuring the connection with the satellite. Difficulty at sea versus land based is that a yacht is constantly moving, the dish antenna needs to be stabilized with respect to the horizon and true north. Small electric motors and sensors keep the dish pointed accurately at a sat, to secure data transfer. Drawbacks are low bandwidth, high latency and higher latitude coverage
A network of Low Earth Orbit (LEO) satellites to provide mobile internet access around the world. The network will eventually consist of 40.000 small satellites, orbiting earth at multiple operational altitudes.
In May 2019 the first 60 satellites were launched successfully with the falcon 9 rocket, to date 422 satellites are orbiting our planet.
Starlink might be capable of reaching 1 Gbps.
By expanding the numbers to thousands of satellites and connecting them in a network, Starlink can ensure global coverage exceeding any other sat network.