Cpt. Says Wagner Left Wood
'To Teach Her a Lesson'
In an interview with TMZ, Lana says Captain Dennis Davern told her several details about Natalie's death ... including that there was a drunken fight between Wagner and Natalie that night in 1981.
Lana claims Wagner -- or RJ, as she calls him -- didn't call her until 2 days after Natalie's death and offered her no explanation, other than ... "it was an accident."
As for the reopening of the investigation, Lana says her sister "deserves the truth" -- and she never bought the official explanation about Natalie and the dinghy ... because she knows her sister was afraid she would die in "dark water."