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 Ð powered by light, any light. Never needs a battery. Caliber number E168.