Stunts in 'San Andreas' look ridiculous without special effects

Disaster movies in which entire cities are leveled by the fury of nature have become a tradition in Hollywood. The latest of these, "San Andreas," was released on May 29 and topped the box office with a solid $54.6 million opening weekend.

To recreate the sensation of California getting completely destroyed, "San Andreas" had to employ a lot of special effects. It's impossible to understand just how heavy the CGI is in a movie like "San Andreas" until you watch it before the effects were put in place.

Luckily, a behind-the-scenes video captures some of the movie's key scenes without the help of effects wizardry.

Some of the clips may make you chuckle a bit, especially at the site of people running and jumping from absolutely nothing. However, it will also make you appreciate just how much summer's biggest blockbusters are a result of visual effects and editing.

Here's a shot of star Alexandra Daddario getting knocked down by the sheer force of nature's fury:

It's a lot funnier to watch acted out without a real quake:

In a scene where people are running through the streets from a sinister dust cloud ...

They're not running from much of anything. 

Instead, many people are strapped to wires, flying through the air. It looks pretty crazy.

Here's a view of the same people from a different angle.

At one point, Dwayne "The Rock" Johnson gets out of his truck and sees that the road in front of him has been split down the middle:

However, when looking at it through one of the monitors, the impact of the earthquake is much less terrifying with the added blue screen.

In a big action sequence, Johnson's character helps pulls his wife up into a helicopter:

This moment loses most of its terror once you see she wasn't as high up off the ground.

However, not everything was done with CGI. 

In one scene, Johnson takes his rescue mission underwater.

Johnson was actually holding his breath and swimming beneath the surface.

Check out the full video below: