At least 367 people have died and 118 are missing after trying to reach Yemen from the Horn of Africa so far this year, the UN refugee agency says.
Most of those who died were forced off the boats by smugglers, drowning in deep waters, said the UNHCR.
Some 8,600 smuggled people have nevertheless arrived in Yemen this year – a 30% fall since 2006.
People are fleeing poverty and unrest, mostly in Somalia or Ethiopia, to seek a better life in the Middle East.
"Many of those who lost their lives, after paying a fee of $50 (£25) to make the perilous voyage, were forced by smugglers to disembark offshore, while still in deep water and drowned trying to swim to shore," the UNHCR said.
"Others were beaten to death by club-wielding smugglers, or attacked by sharks after being thrown overboard. Many bodies were buried on Yemeni beaches by local fishermen."
Many embark in the Somali port of Bossaso, in boats that are often unsafe, at the mercy of ruthless smugglers.
The traffic across the Gulf of Aden is now suspended due to the rough seas at this time of year.
But the UNHCR warns that smuggling continues unabated in the Mediterranean.
"Despite a drop in irregular arrivals in Italy by 31% compared to the first six months of last year, the number of dead and missing – at least 200 in the Strait of Sicily in June alone – shows how dangerous it has become to cross the Mediterranean."
The solution to this crisis, according to the UN agency, lies not only in cracking down on the smugglers, but also in tackling the causes of persecution, poverty and conflict that prompt so many people to flee their homes.