Sun-seekers have been urged to stay away from a beach as thousands flocked to the Dorset coast and a major incident was declared in Bournemouth.
Bournemouth Christchurch and Poole Council said Bournemouth Beach was "stretched to the absolute hilt" on the second day of a UK heatwave.
Dorset Police said there were reports of gridlocked roads, fights and overnight camping.
People were urged to "act responsibly" as temperatures hit the mid-20s.
Traffic built up early on coast-bound roads - including Durdle Door - and people travelled to Bournemouth from as far as Birmingham.
By Thursday evening the Sandbanks peninsula was "heavily congested", the council said, repeating its warning for people to "please stay away".
The ferry service in Sandbanks tweeted: "Again we're struggling to get traffic off the ferry at Poole, for now we hope to carry half loads of vehicles from Studland, but depends on the gridlock in Sandbanks tonight."
A local resident took a photo of the lengthy queue for the Mudeford ferry as beach-goers left for the day.
The council said declaring a major incident meant a "multi-agency emergency response has now been activated to co-ordinate resources across the area to tackle the issues".
England's Chief Medical Officer, Professor Chris Whitty, tweeted in response to Thursday's beach scenes with a warning Covid-19 "will rise again" unless people followed social distancing guidelines.
Council leader Vikki Slade said they were "absolutely appalled at the scenes witnessed on our beaches".
"The irresponsible behaviour and actions of so many people is just shocking and our services are stretched to the absolute hilt trying to keep everyone safe. We have had no choice now but to declare a major incident and initiate an emergency response," she added.
The council said it issued a record 558 parking fines.
It said 33 tonnes of waste was cleaned up along the coastline on Thursday morning, along with eight tonnes collected between the piers on Wednesday.
‘MAJOR INCIDENT’ declared in BOURNEMOUTH - pls stay away.— Tobias Ellwood MP (@Tobias_Ellwood) June 25, 2020
With 1/2 million visitors in Dorset, roads are gridlocked, hindering emergency vehicles & beaches are full - with Dispersal Orders on both piers.
I’ve asked Police Minister to dispatch additional police if Dorset requests pic.twitter.com/YnSpfdXOLc
Bournemouth East MP Tobias Ellwood said he had asked the government to dispatch additional officers to Dorset if needed to deal with traffic and antisocial behaviour.
"It is very sad to see a number of people being selfish and also acting dangerously," he said.
Mr Ellwood said it was "not practical" to close Dorset's beaches altogether but suggested signs warning about overcrowding could be put up at railway stations and on approaching motorways.
He added the government needed to be "dynamic" in its response to beach crowding, otherwise the lockdown would have "been for nothing".
"I'm sorry to see the departure of the No 10 briefings because they would have been perfect for today - for a key figure in No 10 to clarify what is actually happening in Bournemouth and to clarify that message nationally - to say 'please for the moment stay away from all our seafronts'," he said.
Extra police officers have been brought in and security is in place to protect refuse crews who the council said faced "widespread abuse and intimidation" as they emptied overflowing bins.
The Royal Bournemouth Hospital and Poole Hospital confirmed they had declared a "major incident standby".
In a joint statement, the hospital trusts said this was due to "the impact of extremely crowded beaches, traffic gridlock on roads... the number of incidents of public disorder and risks from fire and to public health."
Assistant Chief Constable Sam de Reya, of Dorset Police, said people should stay away from beaches in these "unprecedented times".
"Clearly we are still in a public health crisis and such a significant volume of people heading to one area places a further strain on emergency services resources," she said.
Photographs showed beaches and beauty spots heaving with people on Wednesday, which was the UK's hottest day of the year so far.
David Morley, who lives in Sandbanks, said: "What we saw was a complete breakdown of normal decent behaviour and law and order - it's completely swamping the system."
The chain ferry linking Sandbanks and Studland was unable to carry vehicles late into Wednesday evening because of the gridlock on surrounding roads. There were also reports of illegal overnight camping on Bournemouth beach.
Elsewhere along the coast, police at Hove Lawns seafront put a dispersal order in place after a large gathering.
At the scene, Emily Hudson, BBC South
From Bournemouth pier there are thousands of people as far as the eye can see. Some in the sea on inflatables, others sitting on the sand, there are significant [numbers of] gazebos - there is one group of about 50 people.
One man told me he camped in a tent overnight, a lot of people have come from Birmingham - a six-hour round trip. People were telling me they wanted to get "out and about" after lockdown.
It's incredibly hard to keep social distancing - people are passing each other certainly at less than 2m.
One woman from Birmingham admitted she felt uncomfortable, but said: "You've got to understand, after three months lockdown in the city centre, even seeing the sea is worth it."
Dorset councillor Laura Miller said she was verbally abused and spat at as she directed traffic at Durdle Door on Wednesday.
Roads to the beauty spot were closed after people failed to use the pre-booking parking system.
"Our local industry is dependent on tourism - we're not saying 'don't come', but come here in a safe and managed way. When it's too busy, no-one is having fun," she said.
The car park was approaching capacity again by mid-morning on Thursday.
Current government guidelines state households can drive any distance in England to parks and beaches.
Earlier this month, both Dorset councils called on the government to impose travel restrictions, raising concerns that visitor numbers could increase Covid-19 cases in the county.