Tom Spencer, who lives right behind the chasm, said he noticed it dipping days before.He told Pirate FM: "I reverse out of here every day and I noticed a little dip when I was driving.
Speedboats are common sights around the harbour area in the popular tourist destination, nicknamed 'Padstein' because it is home of celebrity chef Rick Stein.
One woman who did not want to be named said: 'I saw a helicopter come over us and rushed over to see the commotion and saw two ambulances on the beach, they were working on two people who looked in a lot of trouble.'It was all very frantic.
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The motor thing went funny and flipped the boat so everyone flew out and it started circling them all then went through them.'Jo Rawlings of the Maritime and Coastguard agency said: 'Falmouth Coastguard was first contacted at 15.48 this afternoon reporting that six people had been thrown from a speedboat approximately half a mile off Padstow in the Camel Estuary.'The RNLI lifeboats from Rock and Padstow along with the search and rescue helicopters from RNAS Culdrose and RMB Chivenor were sent to the scene.
St Merryn, Newquay and Polzeath Coastguard Rescue Teams have also been involved.
Tom Spencer added: "For me to buy this property, I had to have a mining search done and the houses are fine, there's nothing underneath.
But the reason why they haven't built on this car park is because of this mineshaft".
The emergency services acted pretty quickly and everyone was ushered away so we couldn't see any more, it was probably for our own good because it looked a mess, it was pretty nasty.