Why does coral grow best in moving water?

Why does coral grow best in shallow, clear water? (2marks)
Suggest how the mutualistic relationship between the small animals (within coral that has a hard calcium shell) and the algae inside them is of benefit to both species. (2 marks)
Give one reason why coral that survives higher sea temperatures is under increased threat from predators (1 mark)

The animals in a mutualistic relationship with the coral probably have gills, like fish, so moving water provides them with a constant supply of fresh, oxygenated water for aerobic respiration, and the clearness of the water maximises photosynthesis of algae. If the animals and algae are thriving, the coral will too.

The animals may provide the coral with nutrients, while the algae provide oxygen via photosynthesis.

I'm guessing that the coral in higher temperature waters will be more vulnerable to predation because more of the other aquatic plants will have died, so there is less variety of food for predators, making corals more vulnerable as the predators have fewer/no alternative food sources.