Seiko Prospex collection:
Seiko Prospex: a vivid story that exceeds even the wildest expectations of athletes and adventurers. Unique diver's watches, dynamic pilot watches and specimens with rotating compass ring. No wish is left unanswered. Timepieces with professional specifications to discover the world your way. On land, at sea and in the air. Experience Seiko technology.
A mechanical watch automatically charges itself while worn by converting the wearer's arm and wrist movements into energy. Movement of the watch causes the main spring of the watch to be wound. This spring is the energy source.