IMMIGRATION : More Cubans Make Perilous Crossing : A record number are expected to journey to U.S. on makeshift vessels this year.

Usually the boats are no more than a couple of inner tubes, lashed together with rope and topped by a piece of canvas. Sometimes they are less than that. Last month, six people made it in a blown-up swimming pool float, paddling with plastic oars.

“Most of the craft they’re using to get here are not something the average person would use to go out on a lake,” says Coast Guard Petty Officer Joe Dye. “That tells you they’re somewhat desperate.”

BACKGROUND: Over the last three decades, when there has been almost no legal way for an ordinary Cuban citizen to travel outside the island, one of the most common means of traversing the 90 miles of ocean between Cuba and the United States has also been the most dangerous. Sharks, treacherous Gulf Stream currents, and sudden squalls that can kick up 14-foot waves in minutes are just some of the hazards.

But this year, for a record number of Cubans, trusting one’s life to a makeshift vessel seems a risk worth taking.

Last month alone, 106 Cuban balseros, or rafters, were picked up at sea by the Coast Guard or other ships cruising the Florida Straits. That’s not only the most ever for a single month, but more than double the average yearly total through most of the 1980s.

A new monthly record may be in the making. During the first two weeks of April, the Coast Guard has turned over to Immigration and Naturalization Service officials 78 Cubans rescued at sea. That figure does not include Cubans who reach shore without meeting up with the Coast Guard. Just last week, for example, 27 rafters in three separate groups were rescued by luxury cruise ships. Another 13 made it to Hollywood, north of Miami, and walked to a nearby 7-Eleven store where they asked directions to Hialeah.

Through Monday morning, a total of 250 Cubans had been plucked from the sea or been met by the Coast Guard after landing safely on the Florida shore this year. The figure for all of 1990 was 497. That was a record number. This year the pace is quicker, and the prime sailing season--when wind and currents are most favorable--doesn’t begin for two months. “This used to be a young man’s thing,” says Coast Guardsman Dye of the crossing, which can take two days or 10. “But we’re seeing a lot more women and children now, whole families.”

No one knows how many rafters perish at sea. But each year empty rafts are recovered and survivors often report the deaths of companions.

Rafts aren’t the only means of travel. On March 20, Cuban Air Force Maj. Orestes Lorenzo Perez arrived by MIG-23, flying his Soviet-built jet into the Boca Chica Naval Air Station near Key West.

Other Cubans have obtained visas to visit the United States, and then asked for political asylum, often with considerable fanfare. On March 22, Cuba’s Radio Progreso program director Romel Iglesias, here to visit relatives, defected live over the airways of Miami’s WQBA-AM, the station which calls itself La Cubanisima, the most Cuban.

Five days later, prominent Cuban artist Arturo Cuenca, 35, on a U.S. tour, called a press conference in Miami to announce that he would not be returning. “The revolution has betrayed us all,” he said in explanation.

Since Fidel Castro assumed power 32 years ago, the pace of clandestine emigration from Cuba has been cyclic, reflecting economic and political conditions on the island as well as the length of time since the last authorized exodus. It’s been 11 years this month since the massive Mariel boat lift, in which 125,000 Cubans came here.

“Things are worse in Cuba now than they were,” says Lisandro Perez, a sociologist at Florida International University, “and the level of optimism about the future is low. During hard times in the past, people had the sense that the revolution would get over the hump, that conditions would improve. Now they’re not so sure.”

FORECAST: Perez says he does not see another Mariel taking shape. “That’s too chaotic,” he says. But he does suggest that Castro could be seeking an “escape valve” that serves to relieve internal pressure while bedeviling the United States with a flood of refugees.

That’s what Castro may have had in mind when, during a Havana reception held just hours after Cuenca’s defection, the Cuban president told an Agence France-Presse reporter that he was considering allowing every Cuban over age 18 to travel off the island. That would make some 66% of Cuba’s 10.5 million citizens eligible to leave. The impact here could be stunning.

In a survey of Cuban-Americans last month by Florida International University, 32% of 600 persons questioned said they had relatives on the island who were likely to come to the United States to live if permitted. An agreement between Cuba and the United States allows for 20,000 immigrants a year, but because of Cuban restrictions, only a relative handful actually leave the island legally.