Original provider and dataset credits: Asociación de Naturalistas del Sureste (ANSE).Abstract: Marine megafauna visual surveys from a dedicated research vessel in the southeastern Spanish Mediterranean coast (Western Mediterranean Sea) between 2005 and 2013. The dataset includes 14,577 occurrence records of seabirds, migrant birds, marine turtles, and epipelagic fish, providing broad-scale information of their distributions. The records were made using standardized strip-transect techniques (adapted from Tasker et al. 1984) following linear transects at 5-6 knots with two observers covering a 180° observation arc. Primary observation method was naked eye, supplemented with 8x40 binoculars for species identification. The sightings were recorded and aggregated into 10-minute bins. For each sighting, the following data were recorded: species, total number of individuals, age class (for birds: adult, immature, juvenile), behavior (feeding, traveling, resting, foraging, kleptoparasiting, kleptoparasited, scavenging), and flight direction (when applicable).