Cameron Grace, 17, saw the fish getting close to the swimmers in Forster, New South Wales, Australia.
Fox hosts Geraldo Rivera and Brian Kilmeade debated whether Trump's Iran drone strike was necessary on Friday morning.
Russian Foreign Ministry spokeswoman Maria Zakharova also suggested the U.S. strategy in the Middle East is collapsing.
The White House has been considering how to respond to the weekend's attacks on Saudi oil infrastructure, which both Washington and Riyadh are blaming on Iran.
"I have seen numerous sharks at Werri using drones, but this is the first time I have been able to warn anyone with the speaker system," said operator Christopher Joye, who released the footage online.
The weekend strike on the Saudi Abqaiq facility appears to have dashed any hopes of a detente between Washington and Tehran.
Yemen's Iran-backed Houthi rebels claimed responsibility for drone attacks at the world's largest oil processing facility in Saudi Arabia, military and government spokespersons said Saturday.
Drone footage appears to show FBI agents and other law enforcement officers searching in and around late financier Jeffrey Epstein's lush Little Saint James estate in the U.S. Virgin Islands Monday.
President Donald Trump said Thursday that the USS Boxer has destroyed an Iranian drone in self-defense.
The Ministry of Defense showcased its latest UAV offering at a military fair in Moscow earlier this week.
"He walked us through his decision and it is chilling to watch 40 seconds of his mind at work," Oliver joked.
"At this time we're not going to take any questions, but we're hoping to come back to you guys with some more information later today," the chief Pentagon spokesman said.
"I firmly put responsibility on this administration and the president," California Representative Jackie Speier said.
Wednesday's drone shoot down is the latest in a series of escalations that threaten to push Washington and Tehran into open conflict.
American officials confirmed that a U.S. Navy MQ-4C Triton drone was destroyed by Iranian forces while flying over the Strait of Hormuz.
Houthi rebels in Yemen, backed by Iran, have claimed responsibility for the attack.
President Donald Trump has decided to stop releasing reports on who and what U.S. drones strike outside of active war zones to the public, which he said last month "means the enemy."
President Donald Trump mocked the drone attack during a presidential rally in Venezuela, but it could happen in the U.S. as well.
The Kalashnikov Concern's "controlled bipedal walker" has been turning heads at the Army 2018 show near Moscow.
The drone was "neutralized" and fell into the sea, according to authorities.
According to the Venezuelan government, those arrested worked with other plotters in Miami and Colombia.
The U.S. government was not involved in any way with a Saturday drone explosion at a Venezuelan military event, according to President Donald Trump's national security advisor.
Maduro was unhurt but seven people were injured, according to Venezuela's information minister.
NASA said the U.S. is "one step closer to normalizing unmanned aircraft operations" in commercial airspace.