Seaweed in Cancun Mexico. Sargazo in Cancun, Currently Cancun Mexico has been receiving large amounts of seaweed acrostics shorelines for the past couple of months. However, that is not enough to stop people from enjoying the beaches of Cancun Mexico. In this video, I head to a Cancun beach to go swimming in water filled with seaweed Sargazo with a new Mexican friend I meet on the beaches of Cancun.