Complex sentence: The Griffin family is vacationing at Quagmire's cabin, the family goes swimming in Lake Quahog, but an "oil refinery" is dumping "toxic waste" into the lake.
Split into simpler sentences: The Griffin family is vacationing at Quagmire's cabin. While there, the family goes swimming in Lake Quahog, but an "oil refinery" is dumping "toxic waste" into the lake.