Drone footage of a Tiger Shark, near Ponta da Fragata, Sal, Cape Verde.
The footage itself is not great but, based on the video "Know your sharks from the air - identification tool for drone pilots", by NSW Department of Primary Industries | Fisheries (https://www.youtube.com/watch?v=nxh2Pp5gq3k&t=114s), it looks to me like a Tiger shark due to the long and narrow tail, rounded head, small very curved pectoral fins, etc.
Video provided to me by Oteniel Jorge Monteiro.
Possibly a costal rib from a sea turtle carapace.