Three urban explorers were fined for breaking Covid rules after they got stuck on an abandoned fort in the Thames Estuary and had to be rescued after their boats floated away.
The trio - one of whom had come all the way from Manchester - visited the WWII-era Red Sands Forts near Whitstable and ended up being stuck there overnight.
After failing to flag down passing boats the men eventually accepted they would have to call the Coastguard and were rescued by the RNLI on Sunday morning.
An RNLI captain points to the Red Sands Forts near Whitstable while approaching them on Sunday to rescue three men who had got stuck on themInsurance Loans Mortgage Attorney Credit Lawyer
They were greeted onshore by a landing party of officers from Kent Police who fined them £200 each.
The group decided to visit the Second World War structures - also known as the Maunsell Forts - after seeing them on a TV programme.
After being slated by people on the RNLI's Facebook post, one of the men stepped forward to admit they were 'idiots' who should have never broken the rules.
Ben Marklew offered his 'sincerest apologies' and said he and his two friends had made a large donation to the RNLI.
He wrote: 'I'm one of the idiots that was involved in all of this at the weekend. I'm posting here for two reasons.
'Primarily to apologise and express our gratitude to all the people and organisations involved. Namely the RNLI, HM Coastguard, Port of London Authority and Kent marine police.
'Also to the Redsand Project who work to preserve the forts and don't need kn**heads like us interfering.'
Mr Marklew, who claimed to be an 'adventurer' rather than an urban explorer, said he wanted to 'expel the myths' about what happened.
The men appear to have climbed into the interior of the forts, where they spent the night before being rescuedInsurance Loans Mortgage Attorney Credit Lawyer
A Kent Police boat found the men's inflatables drifting in the sea - leading to local rumours about who had been inside
'We are not foreigners - one of us was from Manchester so that could be classed as foreign, I will let you pass your judgement!' he said.
'Our RHIBs (boats) have been recovered. We did spend the night there. We were not cold. In fact one of us slept in our pants inside a down sleeping bag.
The Red Sands Forts were built in the Thames Estuary at the height of the Second World War in 1943 and still tower above the waves just seven miles off the coast of Whitstable in Kent.
The huge metal Maunsell gun towers, which were constructed to help gunners shoot down Nazi aircraft heading to the houses, factories and docks of London, have been abandoned since they were decommissioned in 1956.
The forts, which are four miles off Whitstable, were named after their designer Guy Maunsell.
The towers are large installations with seven steel platforms, five of which carried guns arranged in a semi-circle around a control centre and accommodation.
Three sets of Maunsell Forts were built in the Estuary to the same design - the Nore forts off the coast of Sheerness, which have now been demolished, and the Red Sands and Shivering Sands forts, further out.