Red Sea coral reefs off the coast of Saudi Arabia (true color image).

The Red Sea contains some of the world’s warmest and saltiest seawater – that's the result of high levels of evaporation by the hot dry climate. Normally the sea is the intense blue-green that you see here, but algal blooms sometimes form and turn the sea a reddish color when they die off. (Image captured by Sentinel-2A in June of this year)

A note for those interested in geology: The Red Sea lies in a fault separating two blocks of Earth’s crust – the Arabian and African plates.