I was onboard a RNXS "Ham" Class minesweeper out of Poole back in the 70s (we were recovering an aircraft propellor for the FAA Museum) when we got talking about the aftermath of "Tiger". One of the crew had been on an MFV out of Portland and said they were picking up casualties for several weeks after - most were wearing life jackets but that had caused their death.
The definitive account is "Channel Firing: The Tragedy of Exercise Tiger" by Nigel Lewis, ISBN 0-670-82398-8.