Three men and a teenager were rescued from the sea by volunteer lifeboat crews after a speedboat capsized off Jaywick in Essex.
A 16 year old boy suffered a broken leg and shoulder as well as hypothermia during the incident on Saturday afternoon.
The other victims were all men in their 30's and 40's.
Clacton's RNLI inshore lifeboats were launched and part of the beach was cleared so the RAF Sea King rescue helicopter could land.
The teenager and another man who suffered hypothermia and chest pains were taken to hospital. They were both kept in overnight before being released.