Mark Rainsley who authored Southwest Sea Kayaking, a UK guide book and who writes an excellent blog with the same name reports:
"Something terrible has happened in South Cornwall. At least twenty-six apparently healthy dolphins have stranded and died. The dolphins appear to have panicked and swum ashore into shallow tidal creeks between Carrick Roads and the Helford River, stranding along about 16 kilometres of coast.
A tragedy of this scale is almost unprecedented in our waters. It’s too early to ascertain the cause, but much is being made of the fact that a Naval Exercise was taking place in the area at the time."