The Vanishing Mile Isle is a mile long sandbar exposed at low tide. Officially named Grenadier Shoal on nautical charts, it has been a popular excursion near Daufuskie Island. Tour companies on Hilton Head have taken guests to explore the bar for years. Treasures found include sand dollars, sea shells and shark teeth among the tidal pools
The key to a successful visit lies in catching the right low tide, a phenomenon that varies daily due to the gravitational pull of the sun and moon. Tides around a quarter moon phase result in weak tidal exchanges, while full or new moons bring larger tidal variances.
Understanding a Tide Chart
Tide charts use “Chart Datum,” which includes terms like “mean high water” and “mean lower low water,” representing average high and low tide depths over a 19-year period. Concerning low tide, the focus is on the “mean lower low water” average. Zero on tide charts signifies the average for these low tides.
Normally, any low tide exceeding +0.50 ft above the average allowed for exploration of the Vanishing Mile Isle. During new or full moons, negative tides exceeding 1.5 feet below average would reveal a vast surface area to explore.
2023: A Year of Changes
Spring 2023 brought unseasonably cool weather to Hilton Head, with strong northeastern winds prevailing throughout April and May. These winds not only kept Hilton Head cool but also had a dramatic impact on the Vanishing Mile Isle. The persistent northeastern winds created strong surf, pounding the shoals for weeks, displacing sand, and smoothing out the sandbar. By the time these winds subsided, the island had lost over a foot of its height. What was once visible with a low +0.50 feet, now required a negative tide of -0.50 feet to be seen.
As summer progressed, traditional southern winds helped rebuild the Vanishing Mile Isle. Tybee Island sits directly south of the sandbar, and helps prevent heavy surf buildup, allowing the sand to gradually stack up and the sandbar to return. While not a complete rebuild, by August, almost 6 inches of lost height had been regained.
However, September brought more northeastern winds, including the effects of Hurricane Idalia, Hurricane Lee, and Tropical Storm Ophelia. These winds further flattened the island, making the situation worse than before.
The Vanishing Island has Vanished!
Even a negative tide of -0.50 feet is insufficient to reveal the sandbar. As October approaches, forecasts continue to predict northeast winds, exacerbating the issue. Consequently, Cross Island Cruises has temporarily suspended its beachcombing excursions to the Vanishing Mile Isle until the end of the year, or when conditions improve. While we aim to provide exceptional experiences, the sandbar currently falls short of expectations. Any interest in this tour should contact us directly for alternative ideas of exploring our waters.
Other companies may continue to operate the tour as usual, but it’s advisable to check with them to ensure they are aware of the loss of exposure or if they have alternative plans in mind. Nobody wants to embark on a 2 to 3-hour boat ride with specific expectations, only to find nothing at the destination.
*****OCTOBER 28 UPDATE******
We have seen an improvement in the height of Vanishing Mile Isle. Tours this weekend with a negative low tide level of -.21 feet did present acceptable areas of exploration. We will continue to operate this tour on a limited basis. If interested in taking a tour, feel free contact us to inquire about certain days of availability.