This sign stands behind the little beach below Puʻukoholā Heiau at Kawaihae. Typically, When a shark is sighted, a temporary warning sign is put up, then removed after a few days. This sign is permanent. The reason for this is that beyond this beach is Pelekane Bay and that’s the site of an underwater heiau dedicated to sharks.
This heiau, called Hale o Kapuni, was built by a chief for whom sharks were considered carriers of the spirits of his ancestors. Human sacrifices were carried out on the beach and afterwards, the bodies were believed to have been placed at the heiau for the sharks. Those days are long gone, but the bay and surrounding area is still home to a large population of sharks, hence the sign.
For more information, go to https://www.nps.gov/puhe/index.htm