Almost everyone who books this coast arrives with a picture in their head of clear green water, and almost everyone finds something else. The sand along US 90 was pumped there by engineers in the early 1950s and it fronts the Mississippi Sound, which is shallow, brackish and usually the colour of strong tea. That is not a failure of the beach. It is what a body of water fed by the Pearl, the Pascagoula and the Mobile river systems looks like. The clear water people came for is real, and it is about twelve miles south, on the far side of the Sound, breaking on the Gulf shore of a barrier island you can only reach by boat.
That island is Ship Island, and it belongs to Gulf Islands National Seashore. There is no bridge to it and no road on it. A passenger ferry run by an authorised Park Service concessionaire sails from Jones Park in Gulfport, which is a twenty-minute drive west along the beach road from the Biloxi Lighthouse, and that detail catches people out every season: the boat does not leave from Biloxi. Service runs from around the middle of March to the end of October. Outside that window there is no public way to the island at all, and a February visitor asking how to get out there is going to be disappointed by the answer.
The crossing takes roughly an hour each way. That hour is not dead time. The ferry runs out through the Gulfport ship channel past the container terminal, over water that shallows and deepens in visible bands, and dolphins work the channel edges often enough that most crossings produce a few.
What waits at the other end is stranger and better than a beach. Fort Massachusetts sits at the western tip, a brick coastal fort begun in the late 1850s and not finished until after the Civil War, its walls curving straight out of the sand. A boardwalk crosses the island to the Gulf side, where the swim beach is, and where the water finally does the thing the brochures promised. There are two pavilions, restrooms, outdoor showers, a small concession and chair rental. Beyond that there is nothing: no shops, no shade worth the name, no reliable phone signal, and at present no camping.
Plan it as an expedition rather than an afternoon. The day belongs to the timetable, not to you, and the return sailing is the hardest deadline on this coast.