Petroleum residues of the Deep Horizon Oil Well are anticipated to be rapidly transported north through Florida Strait (the channel located east of Florida and west of the Bahamas) once the material is entrained by the loop current. In the Strait, there are 4 distinctive water masses present (where a water mass is an identifiable body of water that has physical properties distinct from surrounding water) (see figure). At the surface is a relatively low salinity lens (present to 150 m), primarily of South Atlantic (SA) origin (via the loop current) but with strong inputs of freshwater from major rivers (RW) encountered en route (Amazon, Orinoco, and Mississippi Rivers). This lens should exhibit the strongest signature for oil introduced from the Gulf of Mexico. Deeper in the strait are higher salinity water masses originating in the central North Atlantic (Subtropical Underwater; STUW) and the northwest Sargasso Sea (Subtropical Mode Water; STMW), and a low salinity water forming in the far South Atlantic (loosely referred to here as Antarctic Intermediate Water; AAIW) (note map for regions of water mass formation and schematic depictions of transport). Contamination of these deeper water masses is not anticipated, but monitoring for such would be prudent.