I would suspect they are floating on pontoons.
You can see the pillars they are built on in for example https://www.bloomberg.com/news/articles/2022-05-13/china-s-s...
(direct link to image: https://assets.bwbx.io/images/users/iqjWHBFdfxIU/iy93Jvbye2e...)
Solar panels are meant to be water proof, after all they are meant to survive rain storms and melting snow and coastal weather.
alt Hacker News
You can see the pillars they are built on in for example https://www.bloomberg.com/news/articles/2022-05-13/china-s-s...
(direct link to image: https://assets.bwbx.io/images/users/iqjWHBFdfxIU/iy93Jvbye2e...)
Solar panels are meant to be water proof, after all they are meant to survive rain storms and melting snow and coastal weather.