Authorities in Florida have been turning back growing numbers of undocumented Cubans and Haitians arriving by sea in recent weeks as more attempt to seek haven in the US.

Local US residents on jet skis have been helping some of the migrants who attempted to swim ashore after making arduous, life-threateningand days-long journeys in makeshift vessels.

Joe Biden’s turn to the center over immigration comes as Florida’s Republican governor, Ron DeSantis, attempts to plot his own strategy for handling a sensitive situation in the south of his state, calling out national guard troops in a hardline approach.

Last Thursday, the US Coast Guard returned another 177 Cuban migrants to their island nation, while scores of Haitians who swam ashore in Miami were taken into custody by US Customs and Border Protection (CBP).

The coastguard says that since 1 October, it has intercepted and returned more than 4,900 Cubans at sea, compared with about 6,100 in the 12 months to 30 September.

DeSantis, seen as a likely contender for his party’s 2024 presidential nomination, has taken swipes at the White House for what he claims are Biden’s “lawless” immigration policies and perceived open borders.

The Biden administration has hit back, accusing DeSantis of “making a mockery” of the immigration system by staging his own series of political stunts, including an episode last year in which he sent a planeload of mostly Venezuelan migrants to Massachusetts, flying them from Texas at Florida taxpayers’ expense.

The governor is under criminal investigation in Texas and defending a separate lawsuit over the flight, and another to Biden’s home state of Delaware that was canceled, which reports said involved covert operatives linked to DeSantis recruiting migrants at a San Antonio motel with false promises of housing and jobs.

In the latest incidents of migrants attempting to land in south Florida, the TV station WPLG spotted city of Miami marine patrol jet skis rescuing at least two people found swimming in the ocean, and a CBP spokesperson, Michael Selva, said beachgoers on Virginia Key had helped others ashore on Thursday using small boats and jet skis.

Two days earlier, another group of about 25 people made landfall near Fort Lauderdale. Authorities arrested 12, while others ran away.

Increasing numbers of people are risking their lives to reach the US despite stricter policies from the Biden administration intended to deter irregular immigration and increase humanitarian visa numbers for Cubans, and others, to enter legally – but with a high bar to entry unattainable to many of the thousands fleeing existential threats including extreme violence, political oppression, severe poverty and hardships exacerbated by the climate crisis or failed states.

Biden has responded to conservative voices inside the Democratic party and Republicans calling for a tougher stance. But critics say the president’s new “carrot and stick” approach, cracking down on undocumented immigration while appearing to offer an olive branch of more visas, presents obstacles that most migrants would struggle to overcome.

The White House says up to 30,000 people a month from Haiti, Cuba, Nicaragua and Venezuela will be admitted to the US, but only if they apply online, can pay their own airfare and find a financial sponsor.

Writing in the Guardian last week, Moustafa Bayoumi, immigration author and professor of English at Brooklyn College, City University of New York, said Biden was “throwing migrants under the bus”.

“This is a program obviously designed to favor those with means and pre-established connections in the US, and it’s hard to imagine it as anything but meaningless for those forced to flee for their lives without money or planning,” he said.

DeSantis, seeking to build political capital from a president many expect him to challenge for the White House in 2024, accused Biden of under-resourcing the federal response to the Florida arrivals and placing a burden on local law enforcement.

Meanwhile, the impact of the recent increase in migrant landing attempts continues to be felt in south Florida. The Dry Tortugas national park, off the Florida Keys, has only just reopened after being turned into a makeshift processing center for hundreds of people earlier this month.