Genesis Coronado Open Heel Fins, Multiple Colors, NEW! The Coronado has fully adjustable, reliable and convenient squeeze-style quick-release buckles on the fins straps. The fin has a flex limit feature that allows the blade to be easily shaped during the kick to correct position to generate and optimize thrust. The open heel design on this non-vented fin is intended to be worn with dive boots. Fin blade is a composite material combination of rubber and plastic.