I've been on more than 20 cruises. Here are the 9 things I never buy on board.

Cruise ships are my happy place. I've been on more than 20 of them since the '90s, sailing with over five different cruise lines. 

I inevitably spend money each time I'm on board, but there are several things I've learned to avoid buying during my voyages. After all, if I save money during a trip, I can put it toward my next adventure.

Here are the activities and items I never splurge on during cruises.

Most cruise lines sell a selection of over-the-counter medications on board, but you'll probably pay more for them on the ship than you will at your local pharmacy. 

So, I bring my own medicine to treat minor aches and pains, like headaches or scrapes. My must-have items include Advil, Tylenol, Neosporin, and Band-Aids. Antacids, decongestants, and Aleve are also good to bring.

Also, remember to pack any prescription medications in their original packaging. It's important to bring enough to get you through the trip, along with some extra in case you have to extend your stay due to an unforeseen travel obstacle.

The cost of beverages can add up quickly when you're lounging by a ship's pool, sipping piña coladas, and ordering several rounds.

Unlimited drink packages might make sense for cruisers who don't want to worry about their bar bill. If that's the case, I advise purchasing one prior to embarkation, when there are sometimes better pricing incentives. Because the moment you step on the ship, prices usually increase. 

Before you buy a package, figure out how many beverages you'd need to drink each day in order to get your money's worth. Often, it doesn't even out, especially if you're off the ship exploring during port days.

Many cruise lines give travelers a credit-card-sized room key that doubles as an onboard charge card. 

I keep mine in a lanyard around my neck so I don't have to worry about where I should put it as I wander around the ship.

I purchased a pack of five lanyards for $10 from Amazon. On a recent cruise, I saw a staff member selling similar individual ones for about the same price. 

I love art and used to enjoy going to art auctions on the ships. I even bought some pieces way back when. But now, I admire the pieces on display and only purchase one if it really speaks to me. 

Although I've heard some art-selling auctioneers say the works they're selling are an investment, some have also been accused of misrepresenting the value of their wares. 

I usually don't have a strong enough Wi-Fi connection to look into the artists and get a fair appraisal before buying a piece, and I don't want to spend hours of my trip trying to find one.

Buy the art if you love it and are happy with the price, but don't do it to try to fatten your pockets.

It's important to stay hydrated when you're traveling. A lot of people are used to having water with them at all times thanks to popular water bottles like Hydro Flasks and Stanley cups.

Some cruise lines offer water packages, where you can order multiple bottles for a fixed price. I recommend saving some cash by bringing your own water bottle and refilling it at the ships' dining venues and poolside buffets.

It's tempting to document every step I take on my voyages. 

Everywhere I look on cruise ships, I see photographers ready to snap my photo, whether I'm eating dinner in the main dining room or disembarking at a port. The ship staff also sometimes sets up photo backdrops in the evenings.

I've noticed that these photos are often the same size, typically 8 inches by 10 inches, and expensive. 

If you love photos, a package may be worth it, but purchase it prior to embarkation, when you have a chance to find a better deal.

Alternatively, you can snap your own pictures and invest in one or two professional photos on the ship instead of buying an entire package.

Most ships I've been on have salons on board.

It might seem nice to indulge in a manicure or pedicure, but I don't want to spend that time missing out on cruise activities or experiences.

Plus, I've found some onboard salons charge double or triple as much as the ones at home.

If you want a massage to help you relax during your time away, go for it. You might even be able to score better deals than what's listed on the menu if you attend a spa open house or book a treatment when the ship is in port.

Just be prepared for the spa staff to try to upsell you products during or after your treatment. I've found that a lot of these items are marked up, and I've always been able to find them for lower prices at home.

Buy a piece of jewelry or a watch if you love it. However, I've found that prices are often much higher on ships, even if the onboard stores selling them advertise special deals. 

If you're going to buy expensive jewelry, do your research and ensure the items' quality meets your expectations.