As others noted, most marina wifi is pretty poor. You're working with a signal that by its nature is scattered by line of sight obstructions (read: sailboat rigging), so getting a good signal is trouble to start with. Even with an external antenna and radio to connect to the marina's access point (AP), you're dealing with an AP that in many cases is handling signal from multiple clients (your and your dockmates' connections) with a router that can handle limited bandwidth. It's a wonder it works at all, and many are so poor as to be non-functional. That's compounded by the prevalence of boosters, like the Bullet, that most folks set up at the highest transmit strength, just compounding the noise and interference issue. The exception is OnSpot, which, if available, just works. They use a different approach to coverage, and are successful at providing good connection with high bandwidth.
Most marinas provide 2.4gHz coverage, its signal doesn't lend itself to high bandwidth, and there's a narrow frequency band, so it's very subject to interference and noise, both cause data stream errors, and subsequent re-sending of data packets between the client and AP, = SLOW if even useable.
5G has a wider frequency band, not as prevalent in it's use, but increasing, but SIGNIFICANTLY higher bandwidth although at a bit shorter range. So if you have a choice, 5G can provide exponentially higher bandwidth. Signal isn't everything.
If you use a 2.4gHz booster like the bullet, learn how to adjust the transmit power, and reduce it as much as possible. Most connections should be able to function at a 12dB level, perhaps lower. It will reduce the noise level of your connection, improving the throughput, since that is what the goal is. Signal strength is only part of the equation. With multiple client radios screaming at the AP, none end up cutting through the noise, and nobody gets good access (throughput). This is where 5G makes a huge improvement; despite its shorter range, it has the capacity for more data, and since it's not as widely used (right now), it's less crowded. If you're considering a new booster, look into a dual band (2.4G + 5G) antenna and radio to take full advantage of what's available.
And encourage your marina to go with OnSpot. They have it figured out.
