The phrase "warm crystal clear waters" refers to water that is both comfortably warm in temperature and very clear, allowing you to see through it easily. Full definition
A learn to dive holiday is a great way to spend your holiday time, learning in perfect conditions with warm crystal clear waters. (planetdiveholidays.com)
An extensive coral reef features colorful varieties of tropical fish and warm crystal clear waters makes for a great way to spend an afternoon. (wanderingtrader.com)
Lovely warm crystal clear water, what else could you want!!! (twofishdivers.com)