The Bahamas Marine Mammal Research Organisation has a long-term study that has been documenting the occurrence, distribution, and abundance of marine mammals around the islands of The Bahamas since 1991. With more than 1,900 marine mammal encounters in the Bahamas, we are providing the only comprehensive documentation of the marine mammal fauna in this part of the world. Our research is based on the use of systematic boat-based surveys for describing the distribution and habitat use of different marine mammal species. We employ photo-identification techniques for the recognition of individual whales and dolphins, and we have developed new statistical approaches for using these data to determine abundance estimates and occupancy patterns. This photographic sampling is complemented by the collection of skin and faecal samples for molecular genetic analysis, which are being used to assess levels of genetic diversity and investigate the structuring of marine mammal populations. The dataset presented here includes only sea turtle sightings, and other marine mammal strandings and sightings are included in separate datasets in OBIS-SEAMAP. The entire dataset includes 89 stranding records between 1944 and 2005, including 15 species with Cuvier's beaked whale being the most common. Marine mammal sightings data include 444 sightings between 1988 and 2005, including sightings reported from the public. The dataset includes 1,934 BMMS vessel encounters with marine mammals between 1991 and 2005, comprising 20 different species, with the Atlantic bottlenose dolphin representing 60% of all encounters. Finally, the dataset presented here includes 101 sightings of turtles comprising 3 different species between 1991 and 2005.