Generally, you do not need to bring your physical passport to enter Siam Park in Tenerife, provided you have already purchased your tickets. The park entrance typically only requires your printed or digital ticket with a valid QR code. However, there are two important exceptions where identification is mandatory: first, if you have purchased a "Resident Ticket" (available only to residents of the Canary Islands), you must present your official residence card (NIE/DNI) or a passport with a certificate of residence to prove your eligibility for the discounted rate. Second, if you plan to use a credit card for large purchases inside the park or are renting a high-value VIP cabana, a form of ID may be requested to verify the cardholder. For most international tourists, it is safer to leave your passport in your hotel safe and carry a photocopy or a photo of it on your phone as a backup. Since Siam Park is a water park, any physical documents you bring will need to be stored in one of the paid lockers near the entrance to keep them dry and secure while you are on the slides.