Boka Slagbaai is a reef and artificial dive site near Willemstad, in the Netherlands, in the Caribbean Sea. It is accessed from shore, with a minimum depth of 6 metres. The site, known as BNMP #6, is noted for 18th-century cannons found on the seabed. The site lies within Washington Slagbaai National Park. Park rules state that diving is not otherwise possible within the park. Moray eels, schooling fish and spotted eagle rays are resident on the reef, while cephalopods, rays and reef fish are occasionally seen.