Https://www.jordanoutside.com/playa-piskado-playa-grandi-curacao Snorkel with turtles at Playa Piskado on the northwest side of Curacao.
This beach is also known as Playa Grandi.
There is a small parking lot where you drive in, but a larger parking lot that you can access by stairs.
Make sure to bring your own snorkel gear.