Final answer:
Merri most likely experienced the effects of LSD, a hallucinogenic drug known for producing intense visual hallucinations and distorted body sensations.
Step-by-step explanation:
The effects described in the question, including vivid visual hallucinations and feeling separated from one's own body, are characteristic of the effects of LSD (lysergic acid diethylamide), a class of hallucinogenic drug.
LSD is known for its ability to produce altering sensory and perceptual experiences, often resulting in intense visual hallucinations and distorted body sensations. It is one of the most potent mood-altering hallucinogenic drugs.
Other options such as opiates, alcohol, and marijuana do not typically cause the profound alterations in sensory and perceptual experiences described by Merri.