Proof that a dive watch can be fun & functional with the Citizen® ISO-compliant Promaster Professional Diver. With Eco-Drive technology it is powered by light and never needs a battery so you'll never need to open your caseback making sure your watch maintains it factory sealed and water resistant. Featuring our Eco-Drive technology – powered by light any light. Never needs a battery. Caliber number E168. From the Manufacturer Proof that a dive watch can be fun & functional with the Citizen ISO-compliant Promaster Professional Diver. With Eco-Drive technology it is powered by light and never needs a battery so youll never need to open your case back making sure your watch maintains it factory sealed and water resistant.