GULF COAST, U.S. ( TheStreet) -- As BP ( BP) and Transocean ( RIG) attempt to cap and clean the Deepwater Horizon oil spill, the miles-wide slick has already cast a pall over Gulf Coast vacation plans.The good news as of this week is that all Florida beaches -- including Fort Walton, Destin, Okaloosa, Panama City and Pensacola -- are open and a swimming advisory has been lifted for beaches from the Florida-Alabama border to the entrance of the Perdido section of the Gulf Islands National Seashore in Alabama. Sections of the Gulf Islands National Seashore in Mississippi and Florida remain open, but beaches in Grand Isle, Louisiana, remain closed. Meanwhile, local authorities have warned against swimming or fishing off Eastern Dauphin Island, Fort Morgan, Gulf Shores and Orange Beach, Old River and Terry Cove in Alabama and Bayou St. John and Cotton Bayou in Louisiana. Despite these warnings, travel experts are advising vacationers to be meticulous about their research before heading down to the Gulf. "They need to be a little bit careful because a lot of the tourism boards are going to be promotion-heavy and say the beaches are clear when we've seen evidence of tar balls on the beach," says Anne Banas, editor of travel site SmarterTravel. "It's really up the consumer to do their own research, but there's a lot more you can do at these destinations than going to the beach and they need the help." Because the spill just happens to be occurring during hurricane season, travel sites like Orbitz ( OWW) note that most of the affected areas don't typically fall within their top travel destinations around this time of year. Many are considered "drive-time" locations mostly frequented by locals who typically access them by car. However, the drop in business at many Gulf vacation spots has been severe enough to prompt Expedia ( EXPE) and Hotels.com to donate 8% of hotel bookings to the Greater New Orleans Foundation, which is helping with cleanup and recovery. Expedia's affiliate TripAdvisor, meanwhile, is giving its partner hotels and bed-and-breakfast locations in the Gulf three months' worth of free listings to help minimize losses that are already adding up.