Qualidea Code

Qualidea Code is an anime series that aired in 2016 as part of a mixed-media franchise.

Set in a world where humanity is at war against extra-dimensional beings called the "Unknown", all of Japan's children are cryogenically frozen to protect the future of the country. After several decades have passed, the children are awakened after it is deemed that humans are no longer facing extinction, but it is discovered that the children have developed supernatural powers called "World" while in cryogenesis, unique to each person. The story follows the six most powerful children. who are given command of the reclaimed cities and use their powers to defend the strongholds against the continuing invasion.

OP
Kasumi and Ichiya are briefly shirtless.

Episode 2
Everyone wears swimsuits and divide into two teams to find an Unknown that is underwater.