Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
drown (v.)
The verb is a regular weak verb, with principal parts drown, drowned, drowned (both past tense and past participle rhyme with sound), but drown has long had a Substandard drownded form. The error is clearly one of inexperience when encountered in children, but it is a serious shibboleth when it occurs in adult speech.
Most people will understand these three examples as meaning the same thing: He drowned in his pool. He was drowned in his pool. He became drowned in his pool. But the passive voice of the idiom in the second example could also suggest that he was drowned by someone, especially if there is no context to suggest otherwise.
