Abstract Reef-rimmed margins on carbonate platforms are notably heterogeneous. To explore along-strike changes of the north-western margin of Caicos Platform, B.W.I. (near Providenciales), a group of University of Miami and ExxonMobil personnel cooperatively collected field data, including sediment and bottom descriptions as well as Chirp subbottom profile data. The results illustrate the nature of sedimentologic and geomorphic variability along this part of the Caicos platform margin, and these changes are interpreted to reflect the changing nature of energy. The tidal deltas and discontinuous reef on the NW-facing margin suggest this margin is more tidally-influenced. In contrast, the NE-facing margin with a continuous reef and expansive sand apron is more wave-dominated and influenced by swells from the open Atlantic. These results illustrate the nature, scale, and causes of along-strike heterogeneity along one shelf margin, and likely will have ancient analogs.