According to the Wham Baam Teslacam YouTube channel, Ryan was driving his Tesla Model 3 on the highway outside of Mono City, California, with FSD Beta active at 60 mph (96 km/h). As he was driving, a yellow "Flooded" sign appeared on the side of the highway, signaling that the road ahead was partially or completely covered in water.
For some reason, the FSD Beta did not heed the warning and continued driving at 60 mph (96 km/h). More importantly, the driver chose to ignore the sign and delegate responsibility to FSD Beta. Moments later, he would regret not intervening to take control of the vehicle.
He told Wham Baam Teslacam that the car did not decelerate properly as it crossed the stream of water. The footage captured by the vehicle's factory-fitted dashcam confirms this, as we can see the Tesla driving on the flooded highway without reducing speed.
The car aquaplaned and the rear wheels lost traction, causing the vehicle to slide to the left side of the road and plunge into deep water. Fortunately, there was no traffic at the exact moment the Tesla Model 3 crossed into the oncoming lane, or things could have been much more serious.
As a result of the incident, over half of the electric vehicle ended up submerged in the pond. Luckily, Ryan escaped unscathed, but the car might be deemed a complete loss. He intends to file a lawsuit against both the city and Tesla, but his chances of winning seem bleak.
The city fulfilled its duties by putting up the sign, and Tesla has always maintained that users must be prepared to assume control of the car while operating Full Self-Driving Beta.
It seems that the Model 3 owner either relied too heavily on FSD Beta or was curious to observe how the system would behave on the flooded road - both were ill-advised actions.
Source: Wham Baam Teslacam