Chalk Sound is a 5-kilometre tidal lagoon on the southwest coast of Providenciales, studded with dozens of tiny rocky cays covered in low scrub. The water is a vivid, uniform turquoise — so uniform it looks artificial — with a limestone bottom that gives it an almost luminescent quality on sunny mornings. It is one of the most visually striking natural features in the Caribbean.
The sound is best explored by kayak or paddleboard; rentals are available at the road end on the south side, which is also a good vantage point for photographs. The water is calm and shallow enough for swimming in most conditions. The islets are home to nesting seabirds and a few iguanas; some boat operators offer tours that combine Chalk Sound with a beach stop on one of the outer cays.