The 57-year-old woman's father was driving the boat on the Atlantic Ocean side of Vaca Key, Pino said.
"He had absolutely no warning. It just happened instantaneously," Pino said.
The impact likely killed the woman, but it was not immediately clear whether she had any puncture wounds from the ray's barb, Pino said. An autopsy is planned, Pino said.
The stingray died from the impact, officials said.
Spotted eagle rays can weigh 500 pounds and have a wingspan of up to 10 feet. They are known to occasionally jump out of the water but are not aggressive and use the venomous barb at the end of their tail for defense.
The rays are protected in Florida waters and are typically seen swimming on the water's surface.
"Rays jump to escape a predator, give birth and shake off parasites," said Lynn Gear, supervisor of fishes and reptiles at Theater of the Sea in Islamorada. "They do not attack people."