You aren't forced off the ship on port days. Whether you've been to that specific destination before or want a rest day, you're free to stay on board when your ship is in port.
In fact, staying on the ship is a great way to enjoy the amenities with fewer crowds. Additionally, some ships offer special activities and deals for those who remain onboard. For example, if you want a relaxing afternoon in the spa, you can often save money by booking a treatment on a port day. Alternatively, you may want to enjoy the pool deck with fewer crowds compared to a busy sea day.
There's no right or wrong answer when it comes to staying on the cruise ship at port. However, here are 7 reasons you may want to skip going ashore.
You need a day to relax

Even on leisurely cruises to the Bahamas, you will be busier than you think. From poolside competitions to late-night entertainment, there's always something going on.
On sea days, you may find yourself bouncing from one event to the next, whether an afternoon trivia session, wine tasting, or deck party.
There's nothing wrong with staying on the ship while in port since there will be fewer activities. Then, you can prioritize resting and recharging.
It's easier to enjoy the pool deck without fighting for a chair

Because most guests want to get off and explore the port of call, you can take advantage of a relatively empty lido deck.
Instead of waking up early to beat the chair hogs, you can sleep in, have a leisurely breakfast, and then head up to the pool deck when ready. Plus, with fewer people on the lido deck, you can easily grab a drink at the bar without waiting in long lines.
Having been to Mexico a few times before, I opted to stay on the cruise ship in port while sailing on on Wonder of the Seas.

The adults-only Solarium was practically empty around noon, which wasn't the case the day before while at sea. It was nice having our pick of chairs and enjoying the pool and hot tubs with fewer guests around.
Read more: 8 ways to beat the chair hogs on your cruise so you're not fighting for a lounger
Ships offer discounts on spa treatments

Cruise ship spas are expensive! It's not uncommon to see 50-minute massages starting at around $125 per person.
As such, if you want to relax in the spa and save money, consider checking out the spa's port day specials. Sometimes, they offer bundle deals where you can get a massage and facial for a reduced price!
If you have been to a port before, such as Nassau, Cozumel, or a private island, choosing to stay onboard and get pampered in the spa isn't a bad option. There's no wrong way to spend a day on a cruise ship!
There are fewer lines for popular attractions

Mega-ships have more attractions than ever before. Icon of the Seas, for example, has the massive Category 6 Waterpark. Similarly, newer Norwegian ships have go-kart tracks, and Carnival's Excel Class vessels are home to the only roller coasters at sea.
On sea days when there are thousands of guests onboard, the lines for these attractions can be lengthy. While cruise lines are finding creative ways to manage the crowds, one method to beating the crowds is to stay onboard when your ship is in port.
That way, you can ride the water slides repeatedly without a 15- or 20-minute wait between turns. For example, I recently stayed onboard Wonder of the Seas while the mega-ship was docked in Cozumel, Mexico. My partner and I breezed through the waterslides, successfully tackling the Perfect Storm within ten minutes!
Your drink package won't work ashore

Like spa treatments, drink packages aren't cheap. However, with some drink packages costing over $80 per person, per day, it's understandable why you'd want to get your money's worth.
However, drink packages typically don't work ashore. Certain cruise lines, like Royal Caribbean and Celebrity, let passengers use packages at private destinations like CocoCay and Labadee. However, Carnival's CHEERS! Package doesn't work at Half Moon Cay or Celebration Key.
Regardless of which line you're sailing with, you can't use packages in places like Nassau, St. Thomas, Skagway, Barcelona, and Southampton. So, one way to ensure you are getting the full value is to pick a day to stay onboard, rather than going ashore and spending more money on an excursion, food, and drinks.
No schedule to stick to

Excursions have strict meeting times, and you may not want to wake up each morning of your cruise for an 8:30am tour. Plus, if you don't like the excursion you chose, you're stuck with the group for hours.
Staying onboard means you don't have a schedule to stick to. If you set an alarm for 9:00am but decide to sleep in later, there are no penalties!
Alternatively, you can save an activity on the cruise line's app and skip it in favor of more time by the pool or an afternoon nap. By staying onboard and not booking an excursion, the flexibility is all yours!
You can save money for other ports of call

Finally, staying on your ship in port means you can save money for a once-in-a-lifetime excursion in another.
For example, Alaska excursions are more expensive than Caribbean beach days. Helicopter rides can easily cost over $400 per person.
So, there's nothing wrong with choosing to stay on board one day to use your tour budget for a more memorable or unique experience later during the cruise.