While most agree that cruising is great value, there are some additional charges that mean you need to keep a calculator handy.

Most cruise lines readily acknowledge that onboard spending is an important part of their revenue. That means passengers need to keep wary of what they are being charged.

Below, we examine 10 typical extras passengers are frequently offered – and how you can avoid the pitfalls.

1. Excursions

Shore excursions offered by cruise lines can cost three times more than booking the same tour privately and making your own arrangements. And this can really add up if you arrange a shore excursion at most of your ports on a seven-night cruise.

Cruisers who are looking for a hassle-free holiday with everything taken care of might find the pricier cruise line excursion worth it. But there are also seasoned cruisers who have booked their own private shore tours many times and swear by it.

“Reputable providers know full well the importance of returning to the ship on time, and their business reputation depends on it,” says Bob Thomas who has done around 10 cruises. “We have seen so much more of the world travelling in small vehicles rather than 40 person bulk carriers of ship’s herds.”

That said, you’ll have to do your homework to save money while enjoying your holiday. Mr Thomas says that private tours need to be chosen carefully and their past performance checked for reliability.

2. Photographs

The photos taken by cruise photographers come with a fancy price tag. On Carnival, their prints range from $11.99 to $23.99. In the day and age of smartphones, most equipped with a decent camera, you can be the photographer of your own cruise. This way you can also bring home as many photos as you want to. But, we all know that it is easy to forget to take a snap while you’re in the moment. And a professional portrait of you and your family on formal nights is a keepsake no iPhone snap can supplant.

3. Bottled water

Bottled water costs a few dollars a pop on cruises. This is a major rip off like many other tourist spots in the world when you compare it to prices in your local shop. Considering that you’ll need quite a lot of water to stay hydrated especially if you’re on a summer cruise holiday, it will up to a significant pinch in your wallet.

Consider bringing your own bottle and making additional water stops at the buffet or the gym. The tap water on your cruise is also safe to drink unless told otherwise by the crew. So just double check when you get on board and you’re good to go. Also – try the gym.  They often have water coolers – or even free bottled water!

4. Single supplement

Single supplements are charged to cruisers when they travel solo in a double cabin. It often rages between 125 to 200 per cent. We know why the cruise lines do it but it doesn’t make it any less of an impost. When you travel solo without the single supplement, the cruise lines not only lose one person’s cruise fare but also their potential onboard spend.

If you’re planning to cruise solo, look out for lines who offer solo cabins (Norwegian Cruise Line, Holland America Line, Cunard Line), single supplement discounts or better yet wait for offers that waive the solo supplement that luxury lines offer. Or use one of the new apps that help you find a cruise companion.

5. Spa treatments

If your idea of a holiday is to relax and get pampered, the lure of the spa can prove irresistible. But you might find that the facials and massages are dearer than you’re used to on land, and it also usually includes additional gratuities of up to 18 per cent for the services.

But if the spa is a holiday must-have for you, consider scheduling your treatment on a port day as they often offer discounts because the spa is much less busy. We’ve also surveyed the lines to find out who offers the best value spa treatments. Read here to find out.

6. Onboard shops

Don’t forget to pack the basics! Necessities like toothpaste, toiletries and common over-the-counter medication are hugely marked up in the onboard shop. If possible, wait till you’re in port to make such purchases. If you’ve forgotten to pack reading material, most ships also have a library where you can borrow books for free. For duty free shopping, it is not always cheaper than what you can find at home. Make sure you know how much an item costs or compare prices online before making your purchase.

7. Art auctions

Cruise ship art auctions have attracted a questionable reputation over the years. A number of passengers have even filed lawsuits against cruise lines after reaching home and finding out that their art purchase was not quite what they were told it was on board. So make sure you know what you’re buying and how much it is worth before putting your hand up for a bid. Otherwise, you can just show up and soak in the atmosphere and enjoy a couple glasses of free champagne.

8. Drinks and alcohol

Cruise lines charge a healthy premium on drinks and alcohol on board, not unlike a bar or restaurant on land. Hence the drinks package is popular among cruisers and also a highly debated feature on board. Work out if the drinks package is worth it for you, keeping in mind that it comes with many caveats like how all adults in the same cabin have to purchase the package.

9. WiFi

Cruise ship internet has come leap and bounds in recent years as cruise lines figure out that decent internet connection has become more of a necessity rather than a luxury. But that has not changed that WiFi access cost way more at sea than on land. Starting from $12 per day P&O Cruises and up to $50.74 per day on Norwegian Cruise Line. A survey reveals that Australians would only tolerate being without internet access for a maximum of three days.

So to work around it, use WiFi only when you get in port. If you are after the internet to communicate with fellow cruisers on board, lines like Norwegian Cruise Line, Carnival Cruise Line, MSC Cruises and Holland American has web-based service or apps that allow WiFi-enabled devices to chat without having to purchase an internet plan.

10. Room service charge

Some lines like Royal Caribbean and Norwegian Cruise Lines charge a room service fee at all times of the day. With the recent increase, NCL now charges $14.40 (US$9.95) for every room service order. A significant premium if you consider that similar food is available at the buffet if you managed a trip there. Other lines charge for after-hours room service, but with 24/7 pizza available on lines like Carnival Cruise Line, who needs room service?