the one in front is a juvenile; the juvenile's bill is shorter and often paler than in the adult, and the legs can be yellow
Notonectidae swim upside down! At the species level it could be a a Irrorate Backswimmer - Notonecta kirbyi. This insect has 4 wings - 2 colorful, 2 clear. It also has very long middle legs with "brush feet". No visible antenna. I found it dead on my bumper at the McClure's Beach parking lot at Point Reyes National Seashore.
Dozens of these were washed up on the beach