Fifty-seven Somali refugees have drowned off the coast of Yemen after a boat capsized earlier this week.
The UN Refugee Agency says it ran into bad weather.
The sole survivor, who lost his wife and three children on the vessel, swam for a whole day before reaching the Yemeni coast, the UNHCR said.
Yemen is a popular destination for Somalis fleeing fighting at home, but the trip can be risky as smugglers use boats that are not seaworthy.
The UNHCR says this is the largest loss of life between the waters of Somalia and Yemen since 2008, when 114 people drowned after smugglers forced them into the water.
The 42-year-old man who survived grabbed a plastic container from the wreckage to help keep him afloat.
The BBC's East Africa correspondent Will Ross says every day at least one boat is reaching Yemen - packed full of Somalis fleeing the conflict back home.
Over the past 24 hours the fighting in the Somali capital Mogadishu has been heavy.
African Union troops and government soldiers have managed to gain some territory from the Islamist insurgent group al-Shabab.
At least 50 people are reported to have died in the fighting in the past two days.
The Burundian army says six of its peacekeeping troops in Mogadishu were killed on Wednesday.
BBC's Mohamed Mwalimu in Mogadishu says al-Shabab showed photographs of five of the bodies on Thursday and paraded a Burundian soldier they had captured in the clashes.
Al-Shabab, which controls much of the rest of southern Somalia, has been fighting interim government forces for control of Mogadishu in recent months.
Somalia has not had a functioning national government since Siad Barre was ousted 20 years ago.