Their concerns seem as vivid as a front-page picture of Haitians tossed on a beach, and a group of scholars and politicians feel many of the real stories of the Caribbean are lost in monolithic notions about the region.

"The first thing is to give the Caribbean an identity," said political scientist Archie Singham. "This is a chance to redefine the Caribbean and a chance to find a new dialogue with the United States, where unfortunately the cliche's still exist," said writer and scholar Ivan Van Sertima. The need for a change of attitude on the Caribbean brought together a medley of accents and points of view last night to raise funds for the new Caribbean Action Lobby.

Many of the nearly 200 guests, who paid $100 a plate for the dinner at the Shoreham Hotel, the proceeds from which will finance an office here, expressed hope that the lobby would promote "an authenticity" for the Caribbean. Howard Robinson, former U.S. counsul in Martinique, and one of the lobby's founders, said the lack of focus hampered diplomacy. "It makes one's job rather anonymous. You have the Latin American and the Caribbean, Africa and the Caribbean. It's always tacked on," he said.

Some guests represented a bi-cultural identity that one guest described as an additional asset."The immigrant group that lives in two cultures will have its interest reflected," said Singham. Around him were many examples of that double identity, including the keynote speaker Ivan Van Sertima, who grew up in Guyana and now teaches at Rutgers University. Also stressing the need for focus, Van Sertima said the Caribbean people possess, "a volcanic fluidity. Therein lies the great peril and possibility . . . It can inspire original energy once they are understood for what they are."

The Reagan administration's plans for a Caribbean Basin Initiative, and its policy on the Haitian refugees and Cuba, were roundly criticized by some of the organizers. The refugee policy, said Rep. Mervyn Dymally (D-Calif.) is "both illegal and inhumane. I am strongly opposed to the Reagan thrust to change the definiton of the Caribbean to include parts of South America, Central America and Mexico." The Trinidadian-born congressman is chairman of the lobby and chair of a meeting today, where regional officials and politicians, such as former Jamaican prime minister Michael Manley, will discuss policy. Melvin Evans, a former congressman and governor of the Virgin Islands and the ambassador-designate to Trinidad and Tobago, had no comment on the Reagan policy. "It's a little premature to talk about it. I've just come from my first briefing today."