Riding in the rain is not fun. Hydroplaning on four wheels can be a brief moment of terror but is usually just a temporary loss of control. When you only have half the wheels, hydroplaning is more than doubly terrifying. This guy may have been going too fast for the conditions, but it is not like he was being especially careless. That didn't matter as he lost the bike from underneath he and his girlfriend and began sliding down the street. Seeing his passenger sliding into oncoming traffic and towards the wall, the rider thinks fast and pulls her close as they both slide to a stop.
They shave off enough speed before they get to the curb and appear unhurt. Although if you are ever in the same situation, maybe let your passenger get up when they are good and ready after simultaneously crashing and getting a face full of muddy water. Also slow down in the rain and wear a helmet that fits. All good advice.