The UN High Commission for Refugees, UNHCR, in Yemen worked Saturday to provide aid to those who made it to shore.
The organization said the refugees, who were from Somalia, were probably heading towards Sudan.
The IOM said that 80 survivors were rescued and taken to hospital including 24 in "extremely critical" condition. He said the helicopter then stopped firing, but only after it had killed the victims, the Guardian reported.
Coastguard authorities in the Houthi rebel stronghold of Hodeidah said a helicopter gunship attacked the vessel they were travelling on in the Red Sea.
The coalition was assembled by Saudi Arabia in 2015 to fight the Houthis and troops loyal to Ali Abdullah Saleh, the former long-serving president, who have fired missiles into neighbouring Saudi Arabia.
Two security officials in the Yemeni capital, which is controlled by Houthi rebels battling a Saudi-led coalition, said the attack was carried out by a coalition Apache helicopter.
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The Saudi military is engaged in a campaign to drive Houthi rebels out of Yemen's Red Sea coastal region, and it has used its Apaches in the area before: one was shot down near Najran, Saudi Arabia late past year. The coalition is the only party to the conflict with naval and air forces, and rights groups have documented hundreds of airstrikes in which civilians have been killed.
It is not clear yet who is behind the attack.
Saudi Arabia and the other Gulf monarchies, with direct military support from the United States, have been waging a brutal war against Houthi rebels who seized control of much of western Yemen in 2015 and ousted the USA and Saudi-backed president Abd Rabbu Hadi.
The coalition has been backing pro-government forces waging an offensive from the south to retake Yemen's Red Sea coast from Iran-backed Houthi rebels.
Gedi put the death toll at 32, with 27 wounded.
Meanwhile, Amnesty International stated earlier this week that Washington's arming of the coalition could implicate the United States in war crimes and result in even more civilian deaths.