As an avid scuba diver and shark lover, I can in good conscience give the movie 47 Meters Down — starring Mandy Moore and Claire Holt — two thumbs up. I say this knowing that any diver out there will take this to mean one thing: Get out of there quick.

SPOILER WARNING: This article contains spoilers for the movie 47 Meters Down

With more plot holes than hungry sharks, the film — which recently hit theaters — is entertaining, but it portrays scuba diving in a completely sensationalistic fashion under the guise of "realistic horror." It's harmful for new divers, the scuba diving industry as a whole and anyone who loves the ocean.

Now, first, let me say that despite how this movie was marketed, it's really not about killer sharks. There are killer great white sharks — several 20 footers who magically appear after a half-gallon of chum is tossed into the water — and they're portrayed as blood-thirsty killing machines, just as they were in Jaws and every other less successful shark flick made since then. This brand of horror has its own implications for endangered sharks that has been discussed at great length.

The more we associate these important species with fear and death, the more they will disappear. But that's not my main concern, because this film really focuses on the horrors of scuba diving accidents. Rather than sharp teeth and powerful jaws, it's nitrogen bubbles and vanishing air that strike fear into the audience here.

I understand how horror movies work — I love the genre. You have to suspend some disbelief in order for the schtick to work. So I'm not going to gripe about much of the absurdity in this movie; instead, I'll focus on the ins and outs of scuba diving that are presented as fact, but are completely off base. I thought it would be wise to at least try and dispel some of the falsehoods 47 Meters Down projects. There's no way I could catch them all — trust me, any experienced diver would experience this as comedy rather than horror — but here are the 5 most outrageous ways 47 Meters Down gets scuba diving all wrong.

1. Dive Operators Are Not Murderers

The first is simple: Dive operators do, in fact, want you to come up, get back on the boat and live a happy life. In the beginning of 47 Meters Down, Lisa (played by Mandy Moore) and Kate (played by Claire Holt) decide to hop on a "dive boat" that looks more like it was rejected as a prop for a low-budget Wicked Tuna knockoff. Lisa — the more cautious sister — is skeptical of the operation and even protests. She says that you should only do excursions through the hotel's approved partners and to be wary of sketchy tour operators. But Kate, the adventurous one, prods her on.

As the two ladies get ready to board the boat, the captain eyes them both with an inquisitive, cockeyed gaze and asks, "You both know how to scuba dive, right?" While Kate is certified, Lisa bluffs. The captain eyes them for another second, decides that's good enough and lets them aboard.

This is simply not how the world works. No respectable dive operator would ever let a customer dive without approving their credentials. Even 99 percent of the shady operators would refuse to do so. It's a massive risk. No matter what corner of the world you're in, you'd be very hard-pressed to find someone who would willingly send an untrained diver into the water for a quick buck. Dead divers are MUCH more costly.

The premise of the plot centers on great white shark cage diving. Lisa and Kate descend in a rusty cage to 20 feet as sharks visit the chum-filled water. A more responsible and regulated form of this experience is common in several hot spots around the world, notably South Africa and Mexico's Guadalupe Island. (As an aside, many operators will instead either have the cage at the surface so you can breath-hold dive, or let you breathe off a hookah rig that's connected to the boat, so you may not even have to be scuba certified to experience this.)

Some how, some way this operator has brand-spanking-new dive gear, including state-of-the-art full-face masks with radio connectivity (which I have never seen on a recreational operation), but a crumbling boat with a rusty cage. This operator puts a premium on masks, yet uses an ancient, rusty cage that somehow breaks and descends into the abyss.

Don't worry, prospective divers: This simply would never happen. But if you pay attention, properly vet a scuba operation and dive within your limits, you can have amazing shark encounters that will change your perspective on these creatures forever.

2. Compressed Air Doesn't Grow on Trees

Anyone who doesn't understand how air consumption works underwater is going to be very confused watching this film. A quick explainer: Because of water pressure, air compresses the deeper you get and expands as you ascend. So you will go through 200 bars (or about 3,000 PSI) of air much more quickly at 60 feet than you will at 20 feet. In essence: The more shallow you are, the longer you can dive on a tank of air. Now, PADI's limit for recreational diving is 130 feet, and the heroines in this film find themselves around 154 feet, far beyond that limit.

I've never dived to 154 feet, but I would guess that with a full tank you could dive for about 20 minutes before running out of air. And that's my guess for an experienced diver. In this film, Lisa and Kate are completely unexperienced and highly stressed — they would blow through that air within 10 minutes while hyperventilating, constantly talking back and forth, and swimming hard without fins.

The movie should be over within minutes. Cause of death? Drowning. Instead, the underwater sequences last for roughly an hour and the divers are seen on the same tank of air for at least 35 to 40 minutes of that.

Throughout the film, they're seen checking their air, with their consumption varying wildly. In one scene, Lisa loses only 25 bars in 10 minutes of diving that includes intense swimming. Moments later, she loses 13 bars in two minutes of movie time.

It's simply inaccurate, but if you are able to suspend disbelief, it's also confusing.

3. Drowning Is NOT Your Best Option

The majority of the plot is made possible by one rather ridiculous concept: Lisa and Kate should not, under any circumstance, ascend.

The reasoning might be plausible for the uninformed viewer. There are massive sharks that will gobble you up as you ascend, and if you try to do it too quickly, you'll suffer from the bends. ("It's nitrogen bubbles in the brain!" exclaims Kate.) This thought process is the exact opposite of what's taught in a basic Open Water Diver course.

The bends is another term for decompression sickness, or DCS. This is not simply "nitrogen bubbles in the brain," but rather the result of improper decompression after being exposed to high pressure. As you dive, your body tissue absorbs the nitrogen in the gas you're breathing. A proper ascent allows your body to expel this nitrogen slowly, but if you ascend too rapidly, the nitrogen can form bubbles in your tissue of bloodstream. Then, it can makes its way to your spinal chord or brain, but can also present itself in more mild ways.

One of the most basic concepts you'll learn in an Open Water Diver course is that drowning is the absolute worst option. This seems like common sense, but it doesn't seem to apply in 47 Meters Down. The two main characters in this film are trapped at 154 feet because they are under strict orders to stay put. They believe — and are told by the captain — that a shark attack or DCS are worse than running out of air.

This is contrary to what any diver is taught. If you run out of air, you will drown. It's much better to risk a shark attack or deal with the bends than certain death. In this situation, any diver would ascend slowly, make a decompression stop and deal with the risk of a shark attack, which in reality is very low.

But that doesn't make for a very long movie.

To make matters worse, the plot really fouls up the concept of a decompression stop. This is required when you pass the no-decompression limit for a certain depth — basically, if you stay too deep for too long, you have to wait at certain shallower depths in order for nitrogen to properly exit the body.

This is rare for recreational divers, but would be crucial in the event that you spend a solid 50 minutes at 154 feet like these two divers — which is basically impossible.

As Lisa ascends, the boat captain tells her that she must make a deco stop for 5 minutes, a tough task as great whites lurk around. But, Navy dive tables list 5 minutes as the decompression limit for 154 feet. Seeing as though Lisa passed that mark 10 times over, she would have a very lengthy decompression stop. I don't know exactly what it would be, but my guess is she would have to stop at different levels for a total amount easily exceeding a half-hour.

After this laughably short decompression stop, Lisa bolts to the surface — I believe she was stopped around 60 feet — because, hey, once you finish that deco stop, there's no chance you'll get the bends!

Simply put, this type of diving is basically impossible without special equipment.

4. BCs Aren't Car Lifts

This might be nitpicking and — I know, I know — it's important to suspend disbelief somewhat, but divers will get a good laugh out of this. Near the end of the film, Lisa finds herself trapped as her leg is crushed under the massive shark cage. She can't break free to go help her sister, so she makes a bold move: Lisa removes her BC, props it under the cage and inflates it fully. The magical, Hercules-like BC lifts the cage, letting her slip free and make a heroic escape.

ScubaLab performs objective tests on new BCs every year, testing the buoyant lift of each BC. This tells you how much water the BC can displace, and therefore how much weight it can lift on its own. The range for BCs is about 35 to 58 pounds of buoyant lift. A BC could never ever lift a 500-plus pound cage.

(SPOILER ALERT: This scene happens as Lisa is in a dreamlike fantasy induced by nitrogen narcosis, but it's still absurd.)

5. Nitrogen Narcosis — More Underwater Cocktail, Less Underwater Morphine

The movie's big twist deals with a largely inconsequential and misunderstood aspect of scuba diving: nitrogen narcosis. According to the Divers Alert Network, "Nitrogen narcosis is a state of drowsiness and mental impairment that is similar in effect to alcohol intoxication, caused by breathing air under high pressure." This usually rears its head as you descend deeper than 100 feet.

You can put yourself in a comprising situation if your judgment is impaired by narcosis, but, in most cases, it might make you a bit uncomfortable. The general advisement is to understand what's happening to your body and ascend a bit until the effects wear off if you feel uneasy.

In the movie, Lisa makes a heroic escape, reunites with her sister, fights off several sharks and makes her way back to the boat. It's an epic and happy ending.

The only problem? It turns out she's imagining the whole thing, and we return to her at 47 meters, laughing as she experiences the effects of being narked and apparently, a massive hallucination.

This is not at all how nitrogen narcosis affects the body. The feeling is more like the buzz you might feel after a couple of beers than a deep-seated hallucination that might be the result of hard drugs.

And if that's not enough, the movie overblows nitrogen narcosis' effects in more ways than one.

At one point, the boat captain drops down extra air tanks. He admits that he could have done this before, but didn't want to, as changing air tanks can increase your chance of nitrogen narcosis. That's simply not true, and if it was, so what? Is drowning better than feeling tipsy?

All of these absurdities make my head hurt. I think I'm gonna go for a dive to find my happy place.

But first, here are some honorable mentions from the film:

Best of the Rest: Lisa and Kate watch as their friends gear up and dive first, but the men set up their SPGs on the wrong side. ... Despite having zero dive experience, Lisa manages to switch over her gear to a new tank in about 15 seconds while gasping for air. ... Both divers are shown throughout the movie swimming rapidly with no fins while wearing scuba gear, an impressive feat. ... The boat captain drops air tanks 154 feet, and they land right next to the divers, completely unaffected by current.