There are four fundemental means of how a watch works:
   1. By winding it if it is a mechanical style, or by wearing it if it is a "self-winding" type.
    2.  With a traditional Watch Battery.
    3.  With a Self-Winding or Kinetic Rotor System.
    4.  Using a Light - Solar Powered Eco-Drive System.

All of these types of watches share an important characteristic:
To maintain the water resistant feature of the watch - the gaskets of the case should be inspected and re-greased every three to five years - and replaced if needed to assure that they will maintain a barrier between the watch movement and outside moisture, dust, dirt and humidity.

Regardless of the source of power that runs the watch - whether it is Solar, Mechanical, or Battery operated - the only assurance that the watch will maintain it's water resistant qualities is through the maintenance of the plastic and rubber gaskets that seal the case.

Watch cases specifically designed for deep water use usually employ a setting crown that is screwed down into position against the body of the watch case. When hand-tightened against the case, the crown employs additional seals to safeguard against the entry of water at this point.

Be sure to retighten this screw down crown if your watch has this feature. Remember to retighten the crown when resetting the watch during time zone changes, Daylight Savings Time changes, and when resetting the date for months of less than 31 days.

If your watch is a non-diving type, it still requires routine maintenance on the part of the owner. The case gaskets will need to be inspected, lubricated, and changed as necessary. The watch should then go through a water test procedure to test that the work was performed correctly. This test assures the watch technician and the wearer that at the time of the test, the case was watertight.