More than 35,000 migrants have crossed the Channel to the UK so far this year.
Some 539 people were detected on Monday in 13 boats, the Ministry of Defence (MoD) said, taking the provisional total for the year to 35,233.
This is more than the whole of 2021, when 28,561 were recorded.
There have been 2,232 crossings recorded in October so far, PA news agency analysis of Government figures shows.
This includes 1,065 people making the journey on Sunday, marking the fourth time the daily total had topped 1,000 in seven weeks.
Crossings continued on Tuesday amid calm conditions at sea.
The latest milestone comes as the Government faces another legal challenge to its plan to send migrants to Rwanda.
Charity Asylum Aid’s case is due to be heard by High Court judges later this week after similar challenges were made last month.
Deportation flights are on hold while the legal disputes continue. The court is expected to give its ruling on all of the cases at the same time, at a later date.
Since former home secretary Priti Patel announced the deal with the east African nation in April, 29,965 people have arrived in the UK after making the journey from France.
Despite this, the number of people arriving here in small boats is still a fraction of those going to mainland Europe.
Data from the UN’s refugee agency shows at least 120,441 people arrived in Europe via the Mediterranean by land and sea last year.
The MoD said its data was taken from “live operational systems” and was subject to change, “including reduction”.