This is an idea I've had for ages because I tried to find a fic like this and couldn't, so I knew what I had to do! It's set a few months after Blood of Olympus and there's one spoiler for ToA (but chances are you probably know already). I do not own PJO - Uncle Rick does.

It had been a long week at Camp Jupiter, but thankfully Friday had come at last. Frank and Hazel were strolling up into New Rome for the evening. Frank was filling Hazel in on everything he and Reyna had been up to as praetors, and she was telling him all about her time as Centurion of the Fifth Cohort. As they entered the city centre, Hazel tapped Frank's arm and pointed.

'Hey look, it's Percy and Annabeth!'

The pair glanced over to where their friends were sitting by a fountain. They were deep in discussion about something – and Percy didn't seem happy about it. As Frank and Hazel approached, they caught snatches of the conversation.

'I'm the only demigod who can go underwater. I don't see why they can't just send Triton or some other merman to do it.'

Frank frowned. That wasn't true. He could go underwater. Had Percy forgotten their adventures together?

'Me neither,' Annabeth was saying. 'But you can't say no to your dad.'

Hazel and Frank exchanged a curious look.

'I wonder what they're on about,' Hazel thought out loud.

They approached. The couple spotted them and momentarily forgot about whatever was bothering them.

'Frank, Hazel! How's it going?' asked Annabeth.

'We're great! It's so lovely to see you!' Hazel exclaimed.

When they had all greeted each other, Frank said:

'Percy – you're not the only demigod who can go underwater. I can too, remember?'

Percy slapped his forehead.

'Oh yeah, duh! How could I forget seeing you as a giant goldfish?'

'Or a crazy dolphin,' Annabeth added.

Frank blushed a little.

'I'm never gonna live the goldfish thing down, am I?'

'I'm afraid not,' said Hazel. 'I wish I could have been there to see it. It sounded funny.'

She giggled. Frank pouted at her, and then turned back to Percy.

'Anyway – what are you guys talking about?'

'My dad wants me to go under the ocean and help sort out some problem,' Percy told them, rolling his sea-green eyes. 'Tyson told me. He says they want it dealt with tomorrow. But Annabeth and I were hoping to go to the New Rome University open day. That's why we're here.'

'That's rather inconvenient,' said Hazel.

'That's one way of putting it,' said Percy.

'Hmm…what actually is the problem?' Frank enquired. An idea was starting to form in his mind.

'The thing is, Dad's been having some trouble from Porky and Kate.'

Frank shuddered.

'Those two? I thought we'd seen the last of them.'

'Me too, but obviously not.'

'Excuse me, but who are Porky and Kate?' Hazel asked.

'Their real names are Phorcys and Keto,' said Annabeth, rolling her eyes. 'An old sea god, and his sister, the goddess of sea monsters.'

'That's not what it said on their name tags,' Percy retorted. 'And those two tried to turn Frank and me into an aquarium exhibit – I'll call them whatever I want. I've actually got some other names in mind, like…'

Frank was about to cover Hazel's ears when Annabeth interrupted her boyfriend.

'Why don't you explain to these two what's actually going on, Seaweed Brain?'

Percy sighed.

'So basically…those two are majorly bummed that we escaped their little monster exhibit, and that we defeated Gaia and all that. Chiron's cousins, the Ichthyocentaurs, sent this dude called Bill to free the sea creatures from that aquarium, which is great and all, but Porky and Kate managed to slip back into the ocean while all the gods were incapacitated. So they've been hiding away, sending their monsters to attack Dad's palace, which is still being rebuilt from when it got completely destroyed during the war with Kronos. You remember Shrimpzilla?'

'It's called the Skolopendra,' said Annabeth.

This time, Hazel and Frank both shuddered.

'Whatever it's called,' said Frank, 'I don't blame you for not wanting to go near it again. It nearly drowned us all. Well, apart from you, obviously.'

'Yeah, it's not an ideal situation. They've been trying to defend the place, but they want the help of someone more powerful – like a demigod.'

'Like you,' said Hazel. 'But you don't want to go.'

'I don't want any more crazy quests. Especially now I've just found out Mom's having a baby.'

'A baby?' Hazel gave a delighted squeal. 'That's wonderful!'

Percy smiled.

'Yeah. It's pretty cool. And it means I want to stay out of trouble. I won't make a great big brother if I'm eaten by a monster.'

'If you were going to get eaten by a monster, I think you would have by now,' Hazel reasoned. 'And we've defeated this monster before. Surely you can deal with that, right?'

'Oh, I could. Probably. But I've had enough adventures for one lifetime. Several lifetimes, to be honest. I'm sick of being used. I want to get on with my life.'

'So you'd say no even to your own dad?' Frank asked.

Percy raised his eyebrows.

'Would you say no to your dad?'

'…That's a fair point.'

'As you can see,' said Annabeth, 'This is a bit of a dilemma.'

'You can say that again,' Hazel agreed.

'Not if…' Frank began, then trailed off, staring down at the floor.

'Not if…what?' said Annabeth slowly.

'Not if I did it instead.'

The three of them stared at him. He shuffled his feet self-consciously.

'Or not. It's a totally lame idea…forget I said anything…'

'No way!' Percy clapped him on the back. 'Dude, you'd actually be up for it?'

'Well, sure. I'm all in favour of helping Poseidon. I mean, I do owe him a lot and I've always wanted to meet him. Like, properly. So why not?'

'Who'd be praetor while you're gone?' asked Hazel tentatively.

'Well…Reyna. She ran the camp all those months while Jason was away. I'm sure she can do it for one day. I'll run it by her.'

'I'd be happy to fill in for you,' Hazel volunteered. 'I mean, I know it's meant to be a boy and a girl, but…'

'It's only for one day,' said Annabeth. 'You're a great hero, Hazel. I'm sure nobody would mind.'

'Your camp, your rules, right?' Percy laughed.

Frank chuckled.

'Sometimes I'm glad you didn't remain a praetor, Jackson.'

'You're probably right,' he replied. 'Me in charge of anything would be a disaster.'

'So you're going to do it, Frank?' said Annabeth encouragingly.

'If Reyna is happy for me to leave.'

'Wicked! If she says yes, I can pass the message on to Tyson. He thinks you're our brother too, bless him.'

Frank felt a surge of warmth at this, in addition to the butterflies that had just arisen in his stomach. What on earth – or rather, under the sea – had he just agreed to?

Reyna laced her fingers together and rested her chin on her hands as she took in Frank's news.

'This quest does sound dangerous. But not more than anything you've faced before. And Neptune is important – even though we Romans do not care much for him, or for the ocean.'

Percy scowled. Annabeth bit her lip to keep from laughing.

'I can't pass up this chance, Reyna. I'll finally get to meet my ancestor and thank him for my powers.'

'Yes. I understand that this means a lot to you. Just come back in one piece, Zhang.' Reyna said. 'And preferably in human form.'

'I'll do my best.'

'I second that,' said Hazel. 'Reyna – how would you like me to help you out while Frank's gone?'

Reyna smiled.

'That's very honourable of you, Centurion. But I don't think it will be necessary. You have the Fifth Cohort to think of.'

Hazel nodded.

'Yes, Praetor.'

'Hey Frank…' Annabeth suddenly frowned as they began to make their way out of the Principia. 'How are you actually going to get there? To Atlantis, I mean.'

'I can't help you with that,' said Reyna. 'The camp only had one boat, and well, you destroyed it.'

'Yes, because it was barely a boat,' Percy huffed.

'Maybe Arion could take you?' suggested Hazel, amber eyes lighting up at the mention of her companion. 'It makes sense to save your strength for the fight.'

'It does,' Frank agreed, 'But I don't fancy travelling at light-speed with a horse that threatened to trample me to death and called me a silly Chinese Canadian baby-man.'

Reyna raised her eyebrows in amusement.

'He called you a what?'

'Maybe it's not always the best idea to translate for you guys,' Percy laughed. 'Well, I'm gonna Iris-message Tyson now so he can let Dad know you're going instead of me. He could maybe send Rainbow to give you a lift.'

'That's more like it. Rainbow is cool.'

'Awesome.'

That night, Frank gathered some supplies while the others (mainly Annabeth) talked him through what they knew about the Skolopendra, or Shrimpzilla, as Percy still called it. Frank had been knocked overboard before Leo had actually defeated the monster, so he needed every detail of what had happened.

'It attacked the Argo II with those tentacles that came out of its nose,' Annabeth recounted.

'Then it picked up Leo and me,' Hazel continued, 'and Leo shocked it with fire from his hand and threw Greek Fire down its throat, burning it on the inside. Then it swam off.'

'Mmm.' Frank turned over the small vial in his hand. Being a praetor had its advantages – he'd been able to get his hands on some Greek Fire. Summoning regular fire in his hand, however, was not one of his powers.

'You need to turn into something that can hurt it in some way. Maybe with sharp claws or a sting,' said Annabeth.

'But it still has to be a sea creature. Unless you're willing to hold your breath,' said Percy.

'Thanks, Captain Obvious,' Frank joked. 'Actually, I've got something in mind. Something that'll really…shock it. Pun intended.'

He told them his idea. Annabeth was the only one who had heard of it.

'That sounds brilliant, Frank. It should do the trick if you can pull it off.'

'I have complete faith in you.' Hazel reached up on her tiptoes to kiss his cheek. Would he ever not blush when she did that?

'Oh, and by the way, you might have to deal with Triton,' said Percy. 'My brother. He's sooo full of himself.'

'I'm a son of Mars and a praetor,' Frank reasoned. 'I think I can handle him.'

Percy laughed.

'I'm almost tempted to come along just to watch this. It sounds like you've got it in the bag.'

'The open day, Percy,' Annabeth reminded him.

'Yeah, yeah, I'm just kidding, Wise Girl.'

The next day, Frank kissed Hazel goodbye before heading out of Camp Jupiter and down to the coast with Percy. Once at the beach, they would meet Rainbow, who would carry him across the ocean to Atlantis.

Frank wanted to meet Poseidon more than any of the other gods. He'd seen him during the battle with the giants, and during their discussion afterwards, but there had hardly been time for small talk. Otherwise, he might have asked Percy to introduce him. But that would have been awkward with his own dad there, and the rest of the Olympians. This was his best chance.

'Have you thought about what animal you're going to be if you actually meet my dad?' Percy asked.

This stirred Frank out of his thoughts. He'd been so busy thinking about fighting the monster that he hadn't thought that far ahead.

'No. I haven't. Got any ideas?'

'He likes blowfish,' Percy said matter-of-factly. 'He told my stepdad once.'

Frank was curious about how that conversation had come about, but decided not to ask.

They headed down the beach. It was fairly empty. Frank's butterflies returned as he tasted the salty sea air. The ocean was lapping gently against the warm sand, sparkling in the sun. It looked calm and inviting, showing no sign of the dangers that lurked beneath the surface.

The calm was broken only by a horse's head breaking the surface, shining many different colours. It was obvious why Tyson had called him Rainbow.

'Hey, Rainbow.' Percy walked over to the hippocampus, stroked his head, and the horse neighed, flicking his tail and sending droplets everywhere. 'Aww. Tell Tyson I said hey too.'

Frank watched enviously. He had a feeling he was going to spend this whole quest wishing he had Percy's powers.

'Well, good luck, big guy. Hope it goes well. I'd better get back in time for this open day or Annabeth will kill me. I'll see you tonight?'

'Yeah. Tonight.' Frank twisted his fingers together tensely.

'Not nervous, are you?' Percy teased.

'No. I mean…maybe a little. About…you know. The monster.'

'Right.' Percy's sea-green eyes reflected the light bouncing off the ocean. He seemed to know exactly what Frank was really nervous about.

'Dude, I really appreciate you doing this for me, you know? And you have nothing to worry about. Trust me.'

He placed a hand on his shoulder for comfort. Frank managed a smile.

'Thanks, Percy.'

He thought back to their first quest together, when he'd felt that he wasn't nearly as strong or heroic as his friend. He still admired Percy greatly, but that didn't make him feel bad about himself anymore. He was a hero too.

He waded into the water. The ocean tickled his ankles welcomingly. He climbed onto Rainbow's back as Percy headed back up the beach, throwing a wink over his shoulder. It was time to go.