When it comes to cruising, it doesn’t get any bigger than Royal Caribbean’s Oasis-class ships. Comprising Oasis of the Seas, Allure of the Seas and Harmony of the Seas (plus, a yet-unnamed fourth ship that debuts in 2018), the class is the biggest in the world in terms of passenger capacity (up to 5,400 at double occupancy) and gross tonnage (more than 225,000).Royal Caribbean has packed that space with so much to do, it’s impossible to fit it all in over the course of a typical one-week cruise. No doubt you’ll have to make some hard choices about what you can’t miss and what is OK to skip. Worry not! We’re here to help you. Here are seven things not to do on Oasis-class cruise ships.

–By Colleen McDaniel, Senior Executive Editor

Photos: Cruise Critic

This is one of the most popular activities onboard, and it’s also greatly affected by things like weather and rough seas. If the experience is high on your priority list, get to it right away. While everyone else is settling in or grabbing lunch on that first day, head up to Deck 15 to take on the 82-foot zip-line, which flies over the open-air Boardwalk far below. You’ll have much shorter lines, and odds are the weather will cooperate — the ship’s homeport of Fort Lauderdale boasts more than 3,000 hours of sunshine a year.

Or at least, skip it during peak times. The Windjammer serves as the main buffet for all Royal Caribbean ships. On the line’s Oasis-class ships, it feels too small at mealtime. You have plenty of other fee-free options for breakfast, lunch and dinner. For a breakfast, the Boardwalk’s Johnny Rockets has complimentary egg sandwiches, waffles and hash brown nachos (lunch and dinner are $6.95); the Solarium Bistro, within the top-deck Solarium, serves oatmeal, fruit and eggs for breakfast, and salads and light-ish entrees for lunch; the Boardwalk Dog House offers seven kinds of wieners during the day; Cafe Promenade (24 hours) and Sorrento’s (lunch, dinner, late-night) offer sandwiches and pizza, respectively; and Park Cafe has paninis and build-your-own salads.

The Oasis Class offers a wide variety of shows, including Broadway favorites like “Cats” (Oasis), “Mamma Mia” (Allure) and “Grease” (Harmony). Then, there’s the AquaTheater, where acrobatics and diving along with comedy combine for various shows throughout the week. And of course, you have more traditional cabaret-style shows and comedy. With so many options you’d think a seat would be easy to score. Not so much. If you really want to see something, make a reservation for it. (You can make reservations before you even board.) Then, show up at least 35 minutes before showtime to guarantee your reservation. If you don’t have reservations, you might still be able to get in; just get to the theater about 15 minutes before the doors open and cross your fingers. (Many passengers with reservations decide last-minute not to attend, so their seats open up.) It also helps if you’re willing to sit alone or take seats that aren’t in a prime location.

There’s plenty for children to do onboard Oasis-class cruise ships, so don’t worry that they’ll get bored. Sure, there are the kids clubs, where wee ones, tweens and teens can hang with others their age and participate in structured group activities or just chill. But the Boardwalk is also a kids’ paradise, with a free carousel and for-fee spots like the arcade, candy store and ice cream parlor. Royal Caribbean’s partnership with DreamWorks, which brings colorful characters from movies like Shrek and Kung Fu Panda to sea, also extends to the Oasis Class, and families can enjoy trivia, scavenger hunts, and character parades and dining.

You probably know that your cruise fare doesn’t cover all the extras. With vessels the size of the Oasis-class ships, you’ll have plenty of opportunities to spend — a lot, if you let it get out of hand. They’re so flooded with bill-busting offerings (think premium ice cream, extra-charge dining, private surf lessons, Coach bags, fortunes from Zoltar, and more) that it’s easy to forget about the inclusions. You can zip-line, ride a carousel or watch a 3D movie and Broadway show — all for no extra money. In other words, these ships can be enjoyed for the price of the cruise fare alone. Well, that and the cost of a few pints of ale.

6. Don’t think you’re going to be able to find “solitude”

During sunny sea days, these ships are bursting with energy. And noise. Sound from the thumping reggae band surges down from the pool deck to Central Park, the ship’s tree-and-shrub filled “oasis.” Even the pool and deck chairs in the Solarium (reserved for passengers 16 and older) fill with bodies. It’s hard to escape people — but that’s kind of the point. This is a city teeming with families. If you’re looking for relaxation, stay onboard during port days or cruise in November when “full” means closer to 5,400 (double occupancy) than 6,360 (max occupancy). If you truly seek solitude, you can buy a pass for the ship’s capacity-controlled thermal suite, adjacent to the spa. Passes go for $30 a day or $199 for a week. A week-long couples pass is $299.

7. Don’t forego the running track

Oasis-class ships lay claim to what just might be the best running track at sea — or at the very least, the longest. Sure, you can head to the gym and grind out a workout on the ellipticals, stair climbers or treadmills. But why would you want to when you can take in the sea air — in shade! — as you make your way around the track on Deck 5, where 2.4 laps equal a mile. Enjoy the gusts of air conditioning that blast intermittently from the automatic doors along the track, and if you time your run to 15 minutes before the DreamWorks parade, you could jog past a knight or Puss in Boots.