More than 70 children have died attempting the same crossing between Turkey and Greece as three-year-old Syrian boy Alan Kurdi, whose body was found face down on a Turkish beach last month - prompting worldwide outrage about the plight of refugees travelling to Europe.
In a statement issued on Thursday night, Save the Children said the short Aegean Sea crossing was becoming more deadly as winter weather set in.
The statement was issued as an extensive search continues off a Greek island for at least 34 people missing after their boat sank in one of the largest maritime disasters since a massive refugee influx began earlier this year.
Five children, two men and one woman were known to have drowned after the wooden boat, crammed with more than 280 people, sank near the island of Lesbos on Wednesday.
Eight more people drowned at two other locations, bringing the day's total death toll to 16.
"To have the small bodies of babies and children carried ashore or washed up on these idyllic beaches is devastating," said Kate O'Sullivan, part of Save the Children's response team in Lesbos.
"Though the crossing from Turkey to Greece is short, the waters are increasingly dangerous and sadly we're going to see more of these needless deaths."
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According to Save the Children, the International Organization for Migration (IOM) says 69 children died trying to make the crossing from Turkey to Greece between September 2 and October 26. At least five more died in Wednesday night's incident.
The death of Alan Kurdi, the Syrian child from Kobane whose body was photographed washed up on a Turkish beach on September 2, prompted significant debate worldwide about how Europe should deal with the continent's refugee crisis.
"What we need are safe and legal routes for refugees to come to Europe, to stop people who have already suffered so much, losing their lives close to the end their journey," O'Sullivan said.
"I have seen children sleeping in the mud under a flimsy bit of cardboard, and kids shivering with blue lips and hands. We expect the situation to get much worse as winter really bites."
Elsewhere, some 242 people were safely plucked out of the sea after their boat sank about 3km north of Lesbos in rough seas, the Greek coastguard said.
At least 15 children between the ages of three months and 10 years were taken to hospital with hypothermia, according to the UN refugee agency, UNHCR.
More than 500,000 refugees and migrants have entered Greece through its outlying islands since January, travelling on to central and northern Europe as part of the biggest humanitarian crisis on the continent in two decades.
Lesbos, located less than 10km from the coast of Turkey, has been a primary gateway for thousands of refugees crossing the European Union's outermost border. There has been a surge recently as refugees attempt to beat the worsening weather that makes sea crossings more dangerous.
Al Jazeera's John Psaropoulos, reporting from Lesbos, said the death toll was likely to rise from Wednesday's incident.
"Authorities now believe there are very few chances that in these cold October waters - these deep waters between Greece and Turkey - anyone would have survived overnight," he said.
"Two of the survivors told me last night that the sinking of the overcrowded boat occurred when the upper deck collapsed on the lower deck. This caused a large shift in weight which then caused the wooden vessel to capsize."
Source: Al Jazeera And Agencies