People living in seaside resorts have said they are "horrified" by the influx of visitors as temperatures soared ahead of the bank holiday weekend.
Thousands of people have headed to English beaches, with many apparently unconcerned about public health issues.
"Hundreds die every day yet people think it's OK to have a jolly on the beach," a walker in Southend said.
Norfolk Chief Constable Simon Bailey said he feared there was a perception that lockdown was "done and dusted".
'Lack of respect'
Government guidelines in England allow people to travel for fresh air and exercise, as long as they keep two metres (6ft) from anyone they do not live with.
The chief constable of @NorfolkPolice has just told us on @BBCNorfolk that traffic along some of our coastline was at ‘summer bank holiday levels’ yesterday. He’s concerned that too many people have given up on the lockdown. pic.twitter.com/bFikumkXY4— Chris Goreham (@CGoreham) May 21, 2020
Mr Bailey said some parts of Norfolk had seen numbers typical of a regular summer bank holiday and he was concerned at the "lack of respect" for communities who had "done their best to protect themselves".
"We're dealing with far more people heading to the coast, and with the beautiful weather we're having that's not surprising," he added.
"What I do find surprising is a sense that lockdown has been lifted, we can do what we want and the coronavirus challenge has passed.
"I'm really concerned. That is simply not the case."
Bournemouth beach from near my office today!!! Well done people good effort’s 🤬🤷♂️ pic.twitter.com/ZLGtZge0W1— AJ Gritt MBE (@Aj_gritt) May 20, 2020
In Newquay, Cornwall, police said they moved on camper vans that had stayed overnight, while in Bournemouth the borough council urged people to go home if the beach looked too busy.
'Extremely difficult to manage'
In Southend, where photographs appeared to show people crowded on to the beach on Wednesday, councillor Martin Terry said the local authority had been nervous in anticipation of the hot weather.
"We've had days where we've had over 300,000 people come down here," he said.
"A survey was undertaken asking people what's the first thing you want to do when you come out of lockdown and 70% said 'I want to go to the seaside and buy an ice-cream'.
"All we can do is advise people [to] please, please be safe - stay apart and be sensible."
Tony Cox, leader of the Conservative opposition group on Southend Borough Council, said the authority had been "ill-prepared" and that better "people management" would allow them the space to distance.
But Labour council leader Ian Gilbert said the police and council did not have the powers to stop people coming to the area.
"From the moment the government guidelines allowed people to travel, sunbathe and take unlimited exercise we knew it was going to be extremely difficult to manage the situation," he said.
On Thursday morning, BBC reporter Richard Smith spoke to locals in Southend, with one, Simon Stenning, commenting: "I think it's disgusting, and I am so angry because we were told to stay home.
"The message of 'stay alert' is intentionally vague so the government don't have to take any responsibility.
"Hundreds die every day yet people think it's OK to have a jolly on the beach."
Rita, who lives on the seafront at Westcliff, near Southend, said some parts of the resort were so busy "you probably couldn't swing a cat", and she said she avoided the beach when out for a walk.
"It really is bad. The traffic starts at 9 o'clock and it's like a school holiday. We are dreading the bank holiday."
The amount of litter dumped near overflowing bins or strewn across beaches and promenades has also become a matter of concern.
Mark Husmann, who did a beach litter-pick at Tynemouth, North Tyneside, said: "I'm pretty horrified.
"There were masses of people on the beach who seem to think that a global pandemic is less serious in the sunshine."
His Facebook post was echoed by Cathy Kent, who said after seven "glorious" weeks of a litter-free, empty beach at Exmouth in south Devon, the past 10 days had been far busier, with discarded glass bottles a regular find.
In Southsea, Hampshire, Tania Simmons said every bin on her beach walk on Thursday was was "overflowing with rubbish, beer bottles and barbecues", with broken bottles left on the promenade and rubbish strewn across the common.
"It's bloody disgraceful," she added.
Visit Blackpool recently rebranded as "Do Not Visit Blackpool" to discourage visitors as lockdown restrictions were eased.
Hotelier Lyndsay Fieldsend said she had seen a "surge of day-trippers" since then and beaches full of litter.
Council leaders in Sussex, including in Hastings and Brighton, have said the area's amenities are not open to visitors, although Dorset Council said it would reopen some car parks and public toilets in key locations in time for the bank holiday weekend to help cope with demand.