This is the very common black mangrove snail. It’s easy to find and usually abundant. 

The snail meat is about 16% protein. 

Minerals are fairly abundant too: Calcium 10 mg, Magnesium 250 mg, Phosphorus 270 mg, Iron 3.5 mg, Potassium 380 mg, Sodium 70 mg, and Selenium 27 mcg.