a very good documentary,introducing some scientists probe into the deep solution crevice in greenland and peninsula of Yucatan in mexico,very interesting and make me convulse in brain because the deep insides of these solution cavity are really beautiful,the water in these area are so pure and transparent.i used to see some documentary produced by national geographic channel,talking about two guys diving and exploring the caves in Yucatan,but the definition of that documentary is not very high, comparing to the HDTV of this one.when i watch this kind of movies, i will always regret that i choose humanities instead of science which make my orbit of life not very exciting.but "You can't make an omelette without breaking eggs",if i chose science as my major,maybe i would become so busy that i even didn`t have time to watch this documentary and then write this blog.。