The majority of the surf on these west facing coasts is wind swell and suffers in the consequent onshore winds. Having to travel over the shallow North Sea, swells hitting this coasts are also reduced in power.
However they do have swell window which incorporates the occasional long-range groundswell from the north. This doesn't stop both countries having a well established surfing community. Spots on Germany's coast have been regularly surfed since the 1970s and Denmark's since the mid '80s. Water quality isn't great due to industrial activity but it is improving slowly.
Shops supplying surf boards, wetsuits, clothing, leashes, wax, deck pads, fins, DVDs and anything you might need to go surfing.