The unidentified fisherman was treated on the scene, Gaza director of ambulance and emergency services Muawiya Hassanein said.
Medics said the man was lightly injured and successfully treated.
An Israeli military spokeswoman said naval boats observed the vessel heading out of the enforced fishing limit in the northern Strip, and "called several times" warning the boat to return to the area, after which warning shots were fired, she said.
As the fisherman "attempted to evade" Israeli naval boats, the spokeswoman said naval officers saw the fisherman "search his belongings" on the boat at which point he "fell and injured his head" on the side of the boat. The spokeswoman noted that officers reported seeing the fisherman fully conscious following the incident.
Investigations from the Al Mezan Center for Human Rights in Gaza, however, said the fisherman - Hazem Ahmed Jom'a Al Qur’aan, 27 - was injured in the head by shrapnel from the Israeli fire.
The investigation cited medical sources at the Kamal Edwan Hospital, saying his injuries were critical and that e was referred to the Ash-Shifa Hospital in Gaza City for treatment.
In his affidavit to Al Mezan, the organization's report said, fellow fisherman Jamil Hassan Al-Aqraa stated that "as Palestinian fishing boats moved in the sea, and only after moving for 70 meters, Israeli boats opened fire at them directly, causing injury to my relative, Hazem, and damage to his boat (hasaka) severely."
