It's kinesio tape, sort of an alternative to an elastic bandage:
Many divers wear Kinesio Tape on their backs. Kinesio Tape is used to help manage pain for a variety of bone, muscle, and joint issues.
To cover tattoos
Scuba divers also wear lead weights on a belt
they have weight belts
They are bandages to assist compromised muscles, that is all.
K-tape, it helps to relieve sore muscles and joints
29 divers performed in men's 3 meter springboard. 30 divers performed in women's 3 meter springboard. 30 divers performed in men's 10 meter platform. 29 divers performed in women's 10 meter platform. 16 divers performed in men's synchronized 3 meter springboard, women's synchronized 3 meter springboard, men's synchronized 10 meter platform, and women's synchronized 10 meter platform. China won the most diving medals with 11 (7 gold, 1 silver, 3 bronze).
There are women Mexican divers participating.
It is Kinesio tape, used for sore muscles, injuries, and healing. Many Olympic athletes have used it this year.