Why are some beaches have clear water?

Question

Why do some beaches have that turquoise color of water and are so see through clear water and some of them are disgustingly dirty?

Answer 1

Warm, tropical waters have less nutrient in them; and hence less phytoplankton in the water, giving the water a cleaner appearance.

Many tropical resorts are also blessed with white sands (white quartz or white coral), and this also makes the water look cleaner.

Water in the high latitudes, on the other hand are teeming with phytoplankton and Krill which feed off them (hence, they attract whales).