Summary: This study investigates the feeding dynamics of sicklefin devil rays (Mobula tarapacana) and Costa Rican spinner dolphins (Stenella longirostris centroamericana) engaging in a bait ball event. It examines the atypical participation of both predator and prey in the feeding frenzy, shedding light on mobula rays' predatory behaviour despite being primarily filter-feeders. Furthermore, it explores the unexpected presence of myctophids, typically deep-sea dwellers, near the surface during the day and the potential drivers behind this behaviour. Through direct observations, the study aims to elucidate the foraging ecology of mobula rays and the factors influencing the vertical distribution of myctophids in the Eastern Tropical Pacific, particularly in the waters of Costa Rica.