What appeared to be a calm exchange among a group of four men on a boat at the Brooklyn Marina Saturday afternoon turned deadly when one of them took a gun out of his backpack and opened fire. The Post says that the men were fighting over a jet ski while standing along the Venice Marina in Sheepshead Bay, but witnesses say none of the men had even raised their voices before the shots rang out. A police source told the News, "It was low-key, like they were just shooting the breeze." The gunman first shot and wounded 37-year-old Michael Mazzara, an ex-con who has been nabbed on weapons and robbery charges. The shooter then waited out 33-year-old Paul Moghab, who dove in the water when he saw the gun. When Moghab came up for air, the gunman fatally shot hit him in the chest. Mazzara remains in critical condition after being shot in the face. The fourth man apparently hid on the boat during the incident and was unharmed. Police are looking for the shooter, who fled across the Belt Parkway, and is described as a white man in his 30s, wearing a light-colored shirt and camouflage shorts.