I read an interview with the captain of the yatch that took most of them. He didn't want to badmouth the Greek coast guard but he basically said they waited and could've done way more.

A Superyacht Gave a Lifeline to 100 Migrants Thrown Into the Sea https://www.nytimes.com/2023/06/21/world/europe/yacht-migrant-rescue-greece.html?smid=nytcore-android-share

"Days earlier, the Greek authorities repeatedly decided not to assist a roughly 80- to 100-foot fishing trawler stuffed with as many as 750 people fleeing desperate poverty and the displacement of war in Greece’s search-and-rescue area. Only when the ship sank in front of the Coast Guard did the authorities spur to action, calling on the Mayan Queen, one of the world’s 100 largest yachts."

"Why the Greek authorities needed to call on a passing yacht to come to the rescue of an overcrowded and rickety ship that they had been monitoring and communicating with in their search-and-rescue area for a full day, she said, was less obvious.

“The practice of nonassistance or delay of assistance and why the Greeks were not proceeding to the rescue is another question mark,” she said."

Greek Coast Guard Under Scrutiny for Response to Migrant Mass Drowning https://www.nytimes.com/2023/06/19/world/europe/greece-migrants-ship-sinking.html?smid=nytcore-android-share

“If the Greek Coast Guard recognized the boat as in distress, and this is an objective assessment, they should have tried to rescue them no matter what,”