Adrián Simancas , a 24-year-old kayaker in Chile, detailed what it was like to be in the mouth of a humpback whale as his father captured the jarring encounter on video on Feb. 8.

"I could sense I was moving, and I could feel the whale squeezing with the muscles in his mouth." He said that after less than a minute of being in pitch blackness, "I saw light, and he started ...