A cruise ship expert has warned holidaymakers that "90 per cent" of cruise passengers make the same mistake when booking their excursions. According to Lucy Southerton, who worked on cruise ships for a decade, passengers could find themselves unnecessarily out-of-pocket. Lucy explains that quite often passengers find the trips they want cost more once they get onto the ship.

So instead of waiting until you're on holiday to book your excursions, Lucy suggests speaking to your travel agent ahead of departure or by using the cruise line app. She says the price can even be cheaper if you book ahead of time.

On her Cruising as Crew YouTube channel, Lucy said: "If you have researched the port and decided that doing a cruise ship excursion is the right thing for you, then don't wait until you're onboard to book this excursion, which is what 90 percent of people do.

"One, you're going to be stuck in a mammoth queue, because, if you've been on cruises before you will know that the excursion desk is only open at certain times during the day and during these times obviously everyone wants to book their excursions in so, you don't want to be spending your valuable, limited time of our cruise queueing up.

"At least, I don't want to be doing that. And also, excursions sell out extremely quickly, so I've seen a lot of people miss out on once in a lifetime excursions because they assumed that they could book last minute and if that's one of the main things you were looking forward to doing, that can be quite devastating."

Lucy says many passengers assume the excursions offered by their cruise line are the best in the ports they are visiting. She however says the reality is that companies rely on travel companies with "available capacity".

She explains: "This doesn't mean they're offering the best attractions, this means they're offering what's logistically easiest for them to offer."

Instead of merely booking the excursion recommended by the cruise firm, Lucy suggests having a look around the port to see what is available. She says passengers can often save "a lot of money" by booking an excursion with an independent travel operator.

One thing she does warn about however is travel to your ship. Lucy says that one issue with booking a third-party excursion is that you might not be covered should something happen on your journey back to the ship.

She explained: "When I've done something like this, I spend the entire day thinking, 'I wonder if we should start heading back yet just to allow any delays on the trains'. For me, it's just not worth it, I don't enjoy the experience, I don't enjoy where I'm visiting, I spend the whole time thinking, 'Oh my God what if we get stuck in traffic, what if the car breaks down on the way back to the ship, what if we don't make it."