Orville Redenbacher, the agricultural visionary who all but single-handedly revolutionized the American popcorn industry, was found dead yesterday at his home in Coronado, Calif. He was 88.

Mr. Redenbacher was found in a bathtub with a whirlpool in his condominium, where he drowned after a heart attack, the medical examiner's office said.

By his own account he was just "a funny looking farmer with a funny sounding name." But for all his bumpkin appearance, the man with the signature white wavy hair and oversized bow tie was a shrewd agricultural scientist who experimented with hybrids for years before he came up with the first significant genetic improvement in popcorn in more than 5,000 years.

Until Mr. Redenbacher and his partner, Charlie Bowman, achieved their breakthrough in 1965, popcorn was essentially the same product the Iroquois Indians had introduced to the Pilgrims at the first Thanksgiving more than three centuries earlier. And for that matter, the Iroquois variety was virtually unchanged from popcorn archeologists have traced back 5,600 years.