Siam Park is the south coast's blockbuster water park, built on a Thai theme with slides, wave pools, lazy rivers, and a level of polish that explains why so many families plan a whole day around it. It is technically in Costa Adeje, but from Las Américas it is close enough to count as local.
Book ahead in peak season and arrive early if you care about the biggest rides. Even if water parks are not usually your thing, Siam Park is one of the few resort attractions here that genuinely lives up to the hype.