Heist-aan-Zee. Heist-aan-Zee, or Heist, is a town in Knokke-Heist, West Flanders, Belgium. Till 1971 it was a municipality. It was a prominent summer beach resort in the 1890s. It had a beach front lined with hotels and a dike paved walked way on a storm fender. Fishing boats were mooring on the beach, and one could purchase a ticket to bathe in the sea.