Iranian officials say more than 170 people were killed in the strike. Neither the U.S. nor Israel has said it was behind the attack, but the Pentagon is investigating.
The government unveiled items said to have been found on the boat, including high-powered weapons, more than 12,800 pieces of ammunition and 11 pistols.
Defense Secretary Pete Hegseth and Joint Chiefs Chairman Gen. Dan Caine are holding their second briefing on Iran war operations, as the conflict enters its fifth day.
The U.S. Department of State has urged Americans to leave 14 countries across the Middle East amid the widening Iran war, but most flights have been canceled.