As a kid (maybe 6-8) at the beach. My dad was on the shore and I waded out and kept going further and further, until the sand bank fell off and I dropped what felt like 5m underwater and couldn’t find my way back. I wasn’t a bad swimmer but panic set in and I got disoriented. Felt like I was treading water for 15 minutes but it was more like 3 until a family friend saw what was happening and made it out to me to pull me back to the shore.