I went snorkeling at Xel Ha near Talum Mexico. It is an amazing snorkeling experience starting in a mangrove river along surfacing underground rivers and an inlet bay. The water had to have been brackish - many cichlids in the River - More marine in the bay. This is not my video but a pretty good example.[video]http://m.youtube.com/#/watch?v=vneKV2Z9YM4&feature=related[/video]