4 things you should never bring onboard a Disney cruise, according to a travel agent who has booked hundreds of trips

From Disney's Alaska cruises to sailing in the Caribbean, Kathryn Finkelstein told Insider that as a travel agent at MickeyTravels, she's booked all types of sailings for her clients.

She's also embarked on three Disney Cruises with her husband and two children.

In the process, she's learned what works well on cruises — and what doesn't. When it comes to packing for a cruise, she told Insider there are many items she always packs. But much of it can be trial-and-error. Based on her own travels, and the experiences of her clients, she identified four things passengers should skip packing on their next cruise.

While many cruise lines advertise formal nights, you won't find a formal night on shorter three- and four-night Disney cruises, which only have one optional "dress-up" night. The line's seven-day cruises have one formal and one semi-formal night, but these are also optional, according to its website.

Finkelstein added that the majority of Disney cruise dining locations are casual, which means you can keep your shorts and T-shirts on for dinner.

There are a few nicer restaurants with dress codes, like Palo and Remy, so depending on where you plan to eat, dress accordingly, Finkelstein said.

Finkelstein said that when you step into your cruise cabin, you'll find enough beach towels for your entire party.

If those get dirty or if you need additional towels throughout your cruise, the ship's pool decks have a place where you can replace yours and find additional towels.

You can also take the towels off the ship for port days, so there's never a time when you would need towels from home.

Finkelstein said that snorkeling gears — especially fins — can take up a huge portion of your luggage space.

Her suggestion is to spend a little extra money to rent snorkeling gear. Plus, you won't have to lug it around the port all day once you're done using it.

Life jackets take up precious space in your luggage and cruise cabin, so Finkelstein said it's worth it to skip packing life jackets.

"I usually tell clients that Disney has that kind of stuff, and it's not worth taking up that space, especially on a cruise because the rooms are smaller," she said, adding that you can find life jackets on the ship, at ports, and on excursions.