In parts of Spain and the whole Latin America there is a "phonetic phenomenom" called "seseo", which is pronouncing words that contain -z- or soft -c- (-ce, -ci) as the sound of letter -s-. This happens generally in the region of Andalusia and the Canary Islands, as well as in Latin America. Here are some examples of how some words would be pronounced with and without seseo:
zapato (with seseo)
zapato (without seseo)
cerveza (with seseo)
cerveza (without seseo)
contaminación (with seseo)
contaminación (without seseo)