I put solar (usually combination wind/solar) units on remote offshore platforms for years.
Like this?

This does seem a bit more dramatic than simply using a solar grid to assist on a platform.
What I read they are envisioning a huge solar farm floating in the water to power communities.
Huges swaths of water will have considerable changes in temperature and sunlight penetration, which is likely to affect life in the ocean.
Think windmills that chop up bird life as an example.