This USCG-approved, manually operated, single D-cell strobe offers as much as three miles of visibility. On the water, that's a long way. Waterproof to 12 feet, it operates up to 30 hours-8 hours at 60 flashes per minute, then diminishing after that. It also features a pressurized Xenon gas bulb, rust-proof ABS case and stainless-steel lock pin for PFD attachment. It only requires one D-cell battery, which is sold separately. Available for $19.99.