Sarge, the service dog, is a very good boy. He now has Diamond status on Carnival cruises.

On a cruise to Alaska around 2018, Sarge Marcum took advantage of the open air in the Yukon, running around in streams and chasing fish. And his owner had a good time, too.

Sarge, Justin Marcum Sr.'s 14-year-old service dog, was awarded Diamond status in Carnival Cruise Line's Very Important Fun Person Club loyalty program in February, marking over 200 nights at sea (though Marcum said Sarge has sailed far more).

"He loves going to Alaska, and I think it's probably one of the better times he had," said Marcum, a 48-year-old retired U.S. Army military police officer based in Katy, Texas. He has had Sarge since he was a puppy, but after Marcum sustained a brain injury during an explosion, the Belgian Malinois became his service animal in 2013.

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Service dogs are the only canines Carnival allows on board. They are those "individually trained to meet disability-related needs by performing tasks like guiding a blind person, alerting a deaf person, pulling wheelchairs, alerting and protecting a person who is having a seizure, or performing other special tasks," according to the line's website.

Marcum cruises eight or nine times a year, most of the time with Carnival, and he spoke with USA TODAY about bringing Sarge along when he sails. This interview has been edited for length and clarity.

When did you start sailing with Sarge on cruises?

We started about eight years ago.

What was it like cruising for the first time with Sarge?

I mean, it's not painless, but it was pretty easygoing. Carnival actually helped me out a lot with it, told me what paperwork I needed, how to get it, and then they provided a relief area for him. I was a little worried about that, but I would take him to the bathroom every 15 minutes, and he would kind of walk into the relief area. He wasn't really sure what to do, but after about the fifth time I took him down, he was like, "Alright, I guess I'm supposed to go to the bathroom here." And he went and, no accidents, no problems, never.

Editor's note: Carnival sets up a relief area for service dogs in a "non-guest traffic area of the ship," according to its website.

How do you prepare for taking Sarge on a cruise?

First, I contact my (Personal Vacation Planner on Carnival) and make the booking and everything, and then they get me over to Guest Access, and they notate the account. And then they tell me the rules and everything, which, you know, we've got down. They'll tell me to check with the USDA (U.S. Department of Agriculture) for paperwork, and then at that point – I mean, we've done this a while – I go on the USDA website. I find out what their requirements are (for a given destination).

I go to my (USDA accredited) vet, who sees him, checks him out, makes sure he's up to date on all his shots and everything he needs, and then they submit the paperwork to the USDA. And then, the USDA reviews it, signs it and stamps it and mails it back. Now it's all done electronically, usually, so it's pretty easy now.

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How much does the process cost?

I've got a good vet, so she's not expensive. When we first started doing it, it was a little pricey. ... One of the things is the USDA waives the (endorsement fee because Sarge is) a service dog. So they don't charge me on their end.

Sometimes you have to fill out the paperwork (for other countries). ... And then there are a couple of countries that can be a little pricey on their import permit fees.

Editor's note: Getting the documentation various destinations require can cost hundreds of dollars.

As far as packing, are there things that you bring every time?

Yeah, that becomes challenging. That's what I'm doing now. I'm packing for a 16-day cruise (from Miami to Seattle), and so I've got to pack 16 days worth of food for him. ... I'm bringing, between food and treats, about 20 pounds. ... I pack it in my suitcases.

Do you bring toys?

I used to. My son really enjoyed it. I would bring a tennis ball with me, and then (Carnival) would close down the basketball court for us (so we could play fetch). But Sarge is almost 15 now, so he's not quite as energetic as he used to be. So, he gets enough exercise walking throughout the ship every day. But I make sure I bring treats with us and make sure I always have water and a travel bowl that I have on me at all times in case he gets thirsty.

How does he respond to new environments, whether on the ship or once you get off?

He's a people person. He loves especially kids. But believe it or not, when we get to the ship, he's excited, he's pulling, he wants to get on it. And then when we stop and dock somewhere, and we have to clear customs, as soon as we're done clearing customs, he goes crazy. He's like, "Alright, it's time to get off the ship. I need to go find some grass; roll around." He knows it's a vacation, and he treats it that way.

Is there something different about experiencing these travels with Sarge?

I mean, for me, it does. Everybody sees him, and they're like, "Oh, I wish we could bring our dog." I mean, it's actually a lot of work. It's a lot of work from start to finish throughout the day, and it's like having a baby with you. But I mean, we read each other. We've got it down.

To me, it does (make it more special) because I've got my buddy with me, and he enjoys the same things I enjoy. We go to the beach. We go down to Mexico. We go to Mr. Sancho's (Beach Club). He has a great time. They know him there, so there's never a problem. So yeah, I mean, it is. It's a unique experience.

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What is it about Carnival that keeps you coming back?

It's a fun ship. I mean, it's always fun. I've met crew members that I've become friends with that I've known for eight years, and I'll go on certain cruises just to be with those crew members, to see them and interact with them because it's a good time. ...They've always been very accommodating and perfect when it comes to Sarge. I mean, I've never had a problem. They've always stood up for him because not everybody is the dog-friendliest person in the world, and there've been people that have gotten mad because there's a dog there. And they've had my back.

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What is it about cruising in particular that you like?

Well, I mean, it makes it easier with Sarge, because they're accommodating. But you know, it's all in one. I mean, you've got your lodging, your meals, your stops, and you can even go to a variety of places in a short amount of time.

Do you have any tips for people who might want to bring a service dog on a cruise?

Be patient. Be flexible, because I mean, sometimes we get held up getting off the ship because we're waiting on customs to clear us. I mean, it doesn't happen all the time. I remember one time, customs didn't show up for Sarge, so we weren't able to get off the ship. But next time we went to that port, they showed up, they apologized. I mean, it happens. But, you know, be flexible. Just make sure you have all your paperwork and (that they're) up to date on vaccines. I mean, he gets more shots than I do.

Nathan Diller is a consumer travel reporter for USA TODAY based in Nashville. You can reach him at ndiller@usatoday.com.

This article originally appeared on USA TODAY: Carnival gives service dog Sarge its highest cruise loyalty status