A tree is what a lifeguard uses to set up the station where he'll care for the people on the beach and in the water. Trees provide the shade lifeguards need to take care of half-drowned kids and grannies with sand stuck in their bathing suits. That's why they set up their care stations here.
You look closer at the set up and realize the lifeguard is こういち! You know he teaches Japanese but... is こういち really qualified to care for people like this?