CHARLESTON, S.C. -- Offerings of water, honey and rum will be poured along the shores of South Carolina and New York on Saturday, honoring the millions of Africans who died crossing the Atlantic during the slave trade.

Middle Passage Remembrance Day, held on the second Saturday in June, recalls those whose graves are marked only by unbroken waves.

"We must, we must honor our ancestors," said Tony Akeem, who has organized the remembrance at Coney Island, N.Y., for 18 years.

The ceremony grew from a 1989 conference at Medgar Evers College in Brooklyn, N.Y., where Akeem works as a photographer. Other events have spread to Philadelphia, San Francisco, Brazil and Ghana, Akeem said. Most were started by people who have attended the New York event, he said.

It's the 10th year for the South Carolina ceremony. As many as 100 people are expected at a Fort Moultrie dock on Sullivans Island near Charleston.

The first slaves arrived in Charleston in 1670, the same year the Carolina colony was created. Historians estimate nearly 40 percent of the millions of slaves brought to what became the United States passed through Charleston.

Many others never got this far.

"The stories run pretty strong that there were people who realized they were enslaved and would rather drown than be enslaved and when allowed up on the decks, would just jump into the water," said Fran Norton of the Fort Sumter National Monument, which includes Fort Moultrie. "It commemorates those people who gave up their lives for freedom."

Just how many perished in the slave trade will never be known.

"We know that many died of disease because they were packed in the ships like sardines," said Osei Terry Chandler, a project director at a Charleston education facility who is helping organize the South Carolina memorial.

At 11 a.m. Saturday, the water and rum will be poured at the different ceremonies, which generally feature speakers, drum playing and tossing flowers on the water.

"Pouring libations is simply to venerate your ancestors," said Bill Jones, who helps organize the Coney Island ceremony. "It gives the ancestors a cool drink of water, or a little bit of gin or a little bit of rum, whatever you pour the libation with."

"In African spirituality we believe we are in constant contact with our ancestors," he said. "They are not someplace in heaven, they are right here with us."