Phineas, Ferb, and Isabella were lying under the tree in the stepbrothers' backyard. All three were in their swimwear, as the plan had initially been to go swimming but none of them wanted to move from the shade of the tree because of the scorching hot weather. The radio was on, and the three, with nothing better to do, were listening.

"This is Stanky Dog comin' to you on the hottest of the summer! Unless you live at the beach, I say take it easy and do nothin' today. Yup, just find yourself a shady tree-" Simultaneously, the three kids looked up at the tree they were lying under. "-and maybe an aquatic mammal of some sort-" Simultaneously, the three kids looked down at Perry, who was lying next to them. "-and blow the whole day off."

"Come on, guys," Phineas said to his friends. "If we let a little heat stop us from having the best day ever, then the morning DJs win."

Isabella was about to comment when Linda came out into the backyard. "Ooh, boy, it's hot today! So what are you up to?"

"We're gonna make our own beach, right here in the backyard!" answered Phineas enthusiastically.

Linda grinned. "Oh, how cute. Well, I'm off to my spa day. You boys behave yourselves and don't bother your father. He's finally cleaning out the basement."

She left the backyard just as Candace stalked out from the house. "Bye, Mom! Yes! You heard her." She glared at her two brothers and Isabella. "We can't bug dad which makes me in charge... by default." She paused, taking in what they were doing. "Carry on."

"We're gonna need more sand," Phineas commented. "Hey, where's Perry?"

Soon, there was a delivery guy in their backyard, saying, "Aren't you a little young to be a landscape contractor?"

"Yes, yes I am," Phineas answered, signing for the stuff.

Isabella walked up to him. "Hey, Phineas? I've just thought of something. Can me and the Fireside girls be lifeguards? We need to earn our Aquatic-Safety badges."

"Oh, sure." Phineas grinned and took Isabella's hand. "But we can go swimming in the sea at some point, right?"

Isabella also grinned. "Absolutely."

All of a sudden, Candace stormed out of the house.

"Welcome to our beach!" Phineas said warmly.

Candace glanced down at the sandbox. Before Phineas could tell her that that was not their beach, Candace began laughing. "Hah! You call that a beach? This is WAY below your usual standard. This isn't even worth a call to Mom. You know, if you guys ever want to be popular, you're gonna have to stop playing in sandboxes."

Suddenly, a beach ball hit her in the head. "Hey!"

She spun round to see the full extent of Phineas and Ferb's beach. There was an amazingly clear blue sea, with golden sand, and beach huts. It was as if they were on the edge of the actual ocean.

"So Candace, what do you think?"

Phineas didn't stick around to hear what Candace thought. Isabella was pulling him in the direction of the surf shack. And that was how, five minutes later, Phineas found himself surfing the greatest waves he had ever seen, with Isabella perched on his shoulders.

When they got to shore, Phineas noticed that everyone was finally here. He grabbed the microphone from the beach DJ and shouted, "Let's get this beach party started!"

Everyone exploded into enjoying themselves. They paddled in the sea, built sandcastles, and frolicked on the beach. Phineas and Isabella went windsurfing with Ferb driving the boat. "Hey, look! You can see our house from up here!" he called to his girlfriend, who pointed out her own house.

Soon after this…

"Surf contest!" screeched Stanky Dog excitedly. Phineas and Ferb had managed to get the famous DJ to their beach to be the surf contest announcer.

Phineas was reviewing the contestant list when a massive boy stomped his way towards him. "Outta my way, Dinner-bell."

"Hello, Buford," Phineas said passively. "Perhaps you missed the sign."

Buford turned round and read the sign. While he was doing that, the surf contest began.

Stanky Dog provided the commentary. "First up in the surf contest is Bobby Nelson. Oh! And Nelson eats it on five-footer! And there's Django Brown shooting the curl." Django was doing brilliantly well until… "oh, and here comes Buford Van Stomm! Ohh!" Stanky Dog was getting very excited. "He pummels Brown with a Philadelphia traffic stomp! And now he's got him in a Half-Nelson, now a Full-Nelson…oh! And now he's actually beating him with Bobby Nelson!" Phineas winced as Buford used Bobby Nelson to beat Django with. "Here's the scores from our judges." The judges' scores were one, zero, and one eighth. "And Buford doesn't like it one bit." Before anyone could react, Buford had thrown Bobby Nelson at the judges', completely wrecking their table.

Now it was Phineas's turn. After a kiss for luck from Isabella, Phineas went out into the wave. "Next up is Phineas Flynn, and it's great to see a young surfer show such confidence. Uh-oh, what's this?" Buford headed straight for Phineas, but fell through the hologram of him and into the water. "Oh, those kids today and their holographic projections."

Phineas decided to give the judges a taste of what he could do. Stanky Dog loved it. "He's in the pipeline, now he's hangin' ten!" Phineas put his hands down onto the surfboard. "He's hanging twenty!" Phineas held the surfboard by just his teeth, with his body in the air. He could dimly hear Isabella cheering under Stanky Dog's commentary. "He's hangin' thirty-two!" Phineas hung off his surfboard. "Now he's just hangin'! The crowd loves it!" Phineas ran over his surfboard while the plank of wood rotated under him. "I don't think there's a name for that!"

The crowd watching started doing a wave. Phineas decided to improvise and surfed his board over the wave. "The crowd is doing the wave, and Phineas is surfing it!" bellowed Stanky Dog, nearly exploding. Phineas dropped down next to Isabella and waited for the scores. "Let's go to the judges. 10 to the 5th power, infinity, and oh! It seems Phineas Flynn's radical surfing has made judge #3 re-think Einstein's theory of relativity! Cowabunga, laws of nature!"

Isabella ran up to Phineas and hugged him enthusiastically. "That was amazing, Phineas!"

"We have some time for swimming, if you want," offered Phineas. "Want to go swimming?"

Isabella beamed. "Do you really have to ask?"

They were in the middle of their third water fight in the sea when something large and vaguely mountain-shaped rose out of the ocean.

"Is that a volcano?" gasped Isabella.

The volcano erupted, spreading lawn gnomes everywhere.

"GNOOOOOMES!" hollered Stanky Dog, before a gnome hit him.

People began running away and screaming. Phineas took Isabella's hand and they rushed towards the house. Ferb joined them on the way, but the three of them stopped when they saw the beach draining into a giant hole made in the sand. Once everything had been drained away, people crowded round the hole and stared into it.

Perry jumped out of the hole and walked peacefully back towards the house. "Oh, there you are Perry."

Perry chattered.

Phineas addressed the crowd of people. "Well everybody, looks like that's all for today!"

The crowd cheered Phineas and Ferb's names, while they and Isabella entered their backyard and raised the fence, hiding the sand.

"That was great!" Phineas enthused.

"Hey, boys," said Linda as she came into the backyard.

"Hey Mom," said Phineas, as he and Ferb waved.

"So how was your day at the beach?"

Before anyone could answered, Candace ran in, still in her tiki costume, and stood dramatically on the sandbox. "Wait, wait, my kingdom…my Jeremy…it was all so beautiful!" She glared at Phineas and Ferb and made a motion with her hands as if she was strangling them. "WHAT HAVE YOU DONE TO MY PARADISE?!"

She started panting, slightly psychotically.

"Candace, honey," said Linda, looking worried about her daughter. "I think it's time to get you out of the sun for a little while."

She led Candace away.

"I think she had fun," Phineas commented.

Later that day, Phineas, Ferb, and Isabella were lying under the tree again, just like at the start of the day. It was no less hot now than at the beginning of the day.

Stanky Dog's voice came out of the radio. "Stanky Dog here with a special shout-out to my two new pals, Phineas and Ferb, for hosting a beach party that was hot, hot, hot. And speaking of hot, slather on the sunscreen listeners, cause tomorrow's weather calls for another scorcher."

"With a slight chance of scattered lawn gnomes," added Ferb.

Phineas and Isabella laughed.