Yes, shore excursions and popular tours frequently sell out, often months before the actual travel date. This is particularly true for "high-demand" activities with limited capacity, such as scuba diving, helicopter tours, private yacht charters, or swimming with dolphins. For major cruise lines like Royal Caribbean and Celebrity, the most popular excursions in ports like Cozumel, Roatan, or Juneau (Alaska) are often fully booked long before guests even step on the ship. While cruise lines sometimes hold back a very small number of tickets for on-board booking, these are usually claimed within the first hour of the cruise. In 2026, travel experts recommend booking your "must-do" excursions as soon as your cruise or hotel reservation is confirmed. Most bookings are refundable up to 48 hours before the tour, allowing you to secure your spot risk-free. If a tour is sold out, you can occasionally join a waitlist or look for reputable third-party local operators, who often offer similar experiences at a lower price point.