According to the RNLI, lifeboats were sent out to save migrants in the English Channel 290 times last year.
The charity has for the first time made information about its work on migrant crossings public.
The RNLI, which has come under fire for providing a "taxi service" for migrants, claimed to have saved 108 lives in the Channel between the coasts of France and Kent.
According to its chief executive, he didn't apologize for saving lives at sea.
More than 9,000 lifeboats, manned by volunteer crews, were launched in 2022 along the UK and Irish coasts.
Small boat crossings now account for 3% of the RNLI's work after 290 rescue missions for migrants in the English Channel.
When teams are sent to rescue a small boat, they encounter scenes that are becoming more and more traumatic.
The head of lifeboat operations for the RNLI, Simon Ling, stated: "We've had babies thrown at our lifeboats, women screaming, men screaming.
"The situation is very tumultuous. Our crews are taught how to deal with that and how to launch a rescue operation quickly. " .
A lifeboat was called to rescue roughly one in every four of the 1,100 small boats that made the crossing last year, according to a count kept by BBC News.
A boat capsized in December, killing four people, and there were other fatalities. .
Coastguard personnel ask the 238 lifeboat stations owned by the charity for assistance.
The lifeboats that are used to rescue migrants the most frequently are those from nine stations located along the coasts of Sussex and Kent, from Hastings to Whitstable.
Although there has been an increase in donations in response to such public criticism, former UKIP leader Nigel Farage has criticized the RNLI as a "taxi service for illegal immigration.".
The nonprofit organization's annual report for 2022 shows a net increase in income of 30.5 percent, some of which came from higher donations, though costs also increased.
Some of the funds were used to create the "sea stairs," a new floating platform that enables crews to perform water rescues more quickly.
The floating platform was a "game-changer," according to Mr. Ling.
According to him, using the sea stairs made it possible to remove 20 people from the water in 90 seconds as opposed to the traditional rescue method of a sinking small boat, which would take about a minute per person.
The 616 migrants who crossed in small boats on Monday bring the total number of migrants who have made the crossing in 2023 to 8,380.