The Lagoon on Grassy Key is a popular water park in Marathon, Florida, offering 3 attractions for visitors of all ages. The park features 1 thrill ride, 1 family attraction, and a dedicated kids area with 1 splash feature. Thrill-seekers will find plenty to keep their adrenaline pumping, from high-speed slides to exhilarating water rides. Visitors rate The Lagoon on Grassy Key 5.0 out of 5 stars based on 5 reviews. Guests frequently highlight Friendly and helpful staff, Fun and enjoyable water activities, Great food and drink options as standout aspects of the experience. Keys Cable Wakeboard Park, Rhum Runner Aqua Park, Bongo's Botanical Beer Garden For the best experience, plan your visit during weekday mornings to avoid the busiest periods. The Lagoon on Grassy Key is widely considered excellent value for the experience it delivers. Visit on weekdays for a more relaxed experience, arrive early to secure a good spot, and consider trying the brunch at Bongo's for a great start to your day.