The unusual light is a product of the stormy weather and the long 3 minute exposure.
It was very windy on the coast with storm clouds rapidly moving in from the bottom of the frame and obscuring the lighter clouds higher in the sky to give this unusual effect.
When we were kids we used to swim out to this marker - not something I'd try these days even though the Mersey estuary is a lot cleaner these days.
Ref: crosbybeach068pparesize600
Date: 25/01/2009
Location: Crosby, Liverpool