A watercraft fuel cap having the ability to lock in place to a common fuel filler receiver and having a series of unique downward slot designs and necessitating a matching downward slot designed key for tightening or removing the fuel cap from the fuel filler receiver. The fuel cap would also have the ability for a tethering device which attaches the fuel cap and the fuel receiver together. When the fuel cap is removed for the re-fueling process the tether allows for removal but limits the distance the fuel cap can be moved away from the fuel filler receiver. The tether keeps the fuel cap from being missed placed or falling into the water.