Report says no drugs were found at the scene, but that doesn't mean anything.
Could also simply have been the effects of alcohol and the hot water. Back in the 1980s an Army general and his wife both drowned in their hot tub. They were both pretty intoxicated on wine, IIRC.
He was, though, a pretty heavy opiate abuser in years past. Read an article last night that said he had almost died from a ruptured bowl caused by opiate abuse.