The two injured people were hurt when a car mounted the pavement on South Marina Drive.
A witness reported seeing paramedics attending to the two injured people before they were transported to the nearby beach where two air ambulances were waiting.
Martin Brackett, who runs the nearby Marina Guesthouse, said he was first alerted to what had happened when two guests asked for directions to get around the closed road.
"I took a walk to the end and there were three or four ambulances and lots of police and a car on the pavement."
Mr Brackett said the car appeared to have travelled along a wide stretch of pavement for around 12 car lengths before coming to a halt.
He watched as two people were treated for a long period before being loaded into ambulances which were used to transport them the short distance to the beach.
There, the two were carried on stretchers to the waiting air ambulances.
Humberside Police closed the road this morning following the incident, leading to gridlock on the A165.
The force asked people to avoid the area and use the A164 to enter the town.
A picture posted on Twitter by a nearby business showed an air ambulance had landed on the beach.