"Umi no Misaki" written by Fumitsuki Ko, Same author that brought you "Ai yori Aoshi"
Male protagonist, Goto Nagi a high schooler moves to Okutsu shima, an isolated tropical island alone, his father promising to join later. As he lands he meets Narumi Shizuku, one of the three female protagonist, a native to the island to ask direction to Umi no Misaki a cliff overlooking the sea. She generously agrees to guide him to the cliff.
As they enjoy the view Goto jumps to reaches out for his hat blown off by the wind and accidentally falls off into the sea below.
As he sinks into the sea paralyzed from the shock of the fall, he sees Shizuku frantically reaching out for him before he blacks out. Next moment he finds himself on the beach with Shizuku giving him a mouth to mouth resuscitation.
This was the their first encounter.
The other two female protagonists are Nagumo Karin, a neighbor that can't change her habits, resulting to repeatedly encountering Goto in awkward moments and, Mitsurugi Soyogi a hard headed class mate.
The three are holy priestess revered as goddesses to the islanders not to be approached lightly.