7 Reasons Cruise Ships Are Not Like Petri Dishes

It’s almost impossible to read a mainstream media report on cruising without encountering the phrase “floating petri dish.”

Typically, it’s used by lazy journalists to instantly convey to the reader that the ships are breeding grounds for every disease known to mankind.

The only problem? As with most stereotype-based buzzwords, it’s part of a completely false narrative.

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Does this look like a cruise ship to you?

Having had it up to here (you’re going to need to imagine us using several fingers to dramatically indicate our level of fed-upness, which is right around the top of our eyeballs) with the comparison, we decided to address the topic head-on.

So, for any supposed journalists out there preparing to use the analogy in a future piece, let us offer up this simple (and yes, humorous) explanation as to why cruise ships and petri dishes have about as much in common as a dingy and a mega-ship.

1. Cruise ships were not invented by Julius Petri

Gruppenaufnahme von bakteriologischen Kursen im RKI um 1888 A
Photography of participants of bacteriologial courses (including Dr. Julius Richard Petri) at the RKI, around 1888, during the period Petri invented his namesake dish (Photo: Wikimedia Commons)

Though the title of “first cruise ship” is somewhat in dispute, with nearly every major modern cruise line laying claim to creating the cruise phenomenon in one form or another, it’s clear the first pleasure cruise took place in the late 1960s or early 1970s.

Julius Richard Petri, a German scientist, invented the dish that bears his name between 1877 and 1879. Furthermore, Petri died in 1921, making it impossible for him to have invented a cruise ship, or even to have imagined what a modern cruiseliner might look like.

2. There is practically no physical similarity between the two.

harmony of the seas
Royal Caribbean’s Harmony of the Seas is a lot bigger than a Petri dish. (Photo courtesy of Royal Caribbean)

Petri dishes are typically round containers that measure 200 millimeters wide or less. Cruise ships are somewhat rectangular-shaped objects, with most averaging over 1,000 feet long (that’s 304,800 millimeters).

Petri dishes are commonly made of glass, and in the last decade or so, plastic. While cruise ships feature glass and plastic accents, the ship itself is always made of steel.

Anyone who says a cruise ship resembles a Petri dish needs to have their eyes checked.

3. Petri dishes are inexpensive


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Low-cost Petri dishes are available on Amazon.com

It’s possible to purchase 50 Petri dishes on Amazon.com for as little as $15.95. A cruise ship, on the other hand, costs significantly more. The closest resemblance between a petri dish and something you’ll find on a ship that’s similarly priced is a cocktail at Carnival Cruise Line’s Alchemy Bar.

Their mixologists are pretty darn close to scientists and, like what’s often grown in petri dishes, they might just have the cure for what ails you.

4. The floor of a cruise ship isn’t coated with agar

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The pink or blue film on the bottom of a Petri dish is called agar. The floor of a cruise ship is typically covered with tile or carpet

The bottom of a Petri dish is typically coated with a thin layer of agar or agarose gel and left undisturbed for a lengthy period of time to allow germs to grow.

Cruise ship floors are usually made of tile or carpet, and they’re cleaned multiple times per day.

5. Cruise ships don’t live in a lab

Cruise ships sail to the world’s greatest cities. Petri dishes live their entire existence in a boring lab. (Photo courtesy of Norwegian Cruise Line)

Petri dishes rarely leave the laboratory, where scientists spend hours conducting studies and experiments. Cruise ships, on the other hand, spend all their time exploring the world, visiting a new port every day, and as an added bonus, taking a whole lot of happy people along for the ride.

6. There’s been no significant innovation in Petri dishes since they were invented

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You can’t take a SkyRide in a Petri dish, but you can on a cruise ship

“The Petri dish has pretty much always stayed the same – there aren’t a lot of differences that you can make,” said Andrea Sella, an award-winning chemist, broadcaster, and classic science kit and equipment enthusiast.

On the other hand, every new modern cruise ship introduces something new to the mix.

Whether it’s the go karts zipping along the upper deck on Norwegian Bliss, the BOLT roller coaster which thrills guests on Mardi Gras, or the North Star observation pod which literally takes Anthem of the Seas guests to new heights, cruise ships are constantly evolving.

7. Nobody ever trash-talks petri dishes

Talk about irony! While you constantly hear cruise ships referred to as “floating petri dishes,” you never hear petri dishes referred to as laboratory-locked cruise ships. And really, for the first analogy to work, shouldn’t the reverse also hold true? Yet in all the years we’ve been covering the cruise industry, we’ve never once heard anyone — from CEO’s of major cruise lines to passengers — make a disparaging remark about petri dishes.

READ NEXT: Is a Short Cruise Right For You? 5 Reasons to Consider Booking One

This article was originally published on December 29, 2020.

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