I think you are getting two different accidents mixed up.
The 105 crashed into the sea offshore Skegness. Conoco VIP trip if I remember correctly.
It ended up hanging from the floats on one side with the other side torn off. Tail rotor driveshaft failure.
The aircraft that went down on the sand bar while carrying out the seal count in the Wash was Helicopter Hire's Alouette 2. John Crewdson the MD and the observers were all killed.
Main rotor detached.
https://www.gov.uk/aaib-reports/3-19...p-26-june-1983