The go-to for floating solar in the US is Healdsburg reservoir. Marine growth on the float is OK; I think the panel itself is held up out of the water. I guess

The go-to for floating solar in the US is Healdsburg reservoir. Marine growth on the float is OK; I think the panel itself is held up out of the water. I guess a worry could be about heavy things attaching and eventually sinking it, requiring that the carrier be replaced. At least some canals need to remain "navigable", which needs the panels in a frame overhead. I think this is being done in India. The last number I encountered was that there was 3GW of floating solar known installed worldwide, much of it in southeast Asia, e.g. Singapore.