The full heel is usually used for warm water and doesn't require a dive boot. These are not widely used by divers. A heel-strap fin does require a dive boot. The dive boot keeps your feet insulated from the cold water and can protect your feet when walking around on the boat. When buying fins look for fit, stiffness of the blade and size.
Divers use a snorkel to conserve energy and air while on the surface.
A snorkel should be easy to breathe from and have a comfortable mouse piece. Regulator A scuba regulator takes the pressured air from the tank and delivers it to the mouthpiece at the surrounding pressure. Using two stages, the high-pressure air from the tank is reduced to a breathable level. A pressure gauge or air level gauge, depth gauge, and a BC inflator hose are also attached to your regulator. The most important criteria a diver should look for in a regulator is ease of breathing.