Summer is officially over, but we've got one more big trip to the beach still ahead. Monday night's new episode of 9-1-1 begins the two-part tsunami event we've been waiting for, and fans should definitely brace for emotional impact when those waters do arrive.

At the end of Season 3's premiere episode, we saw Buck (Oliver Stark) take Eddie's (Ryan Guzman) son Christopher (Gavin McHugh) to the Santa Monica Pier for a day of fun in the sun. This kid-sitting gig was set up to help lift Buck's spirits after he received the bad news that his blood clots would prevent him from returning to firefighting. The trip seemed to be going well enough ... until Buck and the rest of those at Pacific Park saw that massive tidal wave forming off the coast.

What's ahead is a fight for survival that will leave fans shocked, Stark told TV Guide.

9-1-1 Season 3 Trailer Is a Tidal Wave of Terror

"[This is] something that has never been done, the scale of it, on network television. I think it's hugely ambitious and the fact that it's been pulled off the way it has, I think people are going to watch it and feel like they're watching a blockbuster movie," Stark said. "It's huge in scale, there's a lot of emotion, there's a lot of drama, there's a lot of action. I think everyone's going to be shocked by what they see."

The last shot of the premiere, which held on Buck's stunned face as he realized what was happening, tells us a thousand words about Buck's mindset in that moment. "He's frozen in fear because you can't outrun it," Stark said. "He knows that he's got the blood clots, and he's on blood thinners, and he knows that he's in a very fragile state right now, and I think it's sheer doom."

Stark spent nine days in Mexico to shoot the back-to-back event episodes and more than half of that time involved him being submerged in water. "I'm still not wanting to take a bath. That's how sogged [I was]," he explained. "I would say there were probably five, six days that we were in the water for eight to 10 hours. So, it kind of just became second nature — OK, we're here, jump in the water, and we're off. But I remember one time at the end of the shoot, I went home and took a shower under the water and I just stood there for like 20 minutes in the shower letting warm water drip over me because I was so used to this cold water. It was a lot of time in the water, but we had such good people on the Mexico crew that we were just having fun."

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In the exclusive sneak peek above, we see that Buck is able to reconnect with Christopher after the crash — but we don't know how long that moment will last. Monday's episode will largely focus on Buck's effort to survive the flood, and help Christopher and others in need, and Stark promises it'll be one television event audiences won't soon forget.

"I think it was probably, definitely the highlight of my career. I felt very lucky to get to be a part of something that was so huge and that had so many people's hard work going into it," Stark said of the shoot for the two tsunami-centered episodes. "It was probably the most draining and physically taxing, but also fulfilling thing that I've ever done. I still pinch myself every time I see a clip. I cannot believe I got to be a part of this. I think it's something people will be talking about for a long time."

A second preview from the episode ahead also shows that, on land, the aftermath of the tsunami's impact will also be intense, as Athena (Angela Bassett) is the only help on-hand at a major pile-up scene — no matter how many potential victims are in need.

9-1-1 airs Mondays at 8/7c on Fox.