A coroner says the sooner synthetic cannabis is made illegal, the better.
Tim Scott says the consumption of K2 was a contributing factor in the death of 27-year-old Feilding man Jarrett Simeon, who drowned at Himatangi Beach, in Manawatu, in January.
Mr Scott says smoking the drug before getting in the water is akin to drinking alcohol before going swimming.
He says synthetic cannabis is becoming a common feature at inquests.
While Mr Scott says he cannot say with any accuracy what effect the substance had on Mr Simeon, it was certainly negative.
He says Mr Simeon also swam outside the flags.
Legislation is currently before parliament which would force manufacturers of legal highs to prove they are low risk before they can be sold.