Hint Taken
Numbness.
That's the first thing Annabeth noticed when they were thrown in the lake.
After she finally made that Seaweed Brain realized she liked him, that she REALLY liked him. He wasn't smart enough to realize it a year ago in that stupid forge but she believed he finally got the message.
Annabeth couldn't see anything in the lake but she found Percy once she felt strong arms wrap around her from behind and bubbles surrounding them, forming a bubble with a pop.
He placed hot kisses along her neck while they were lying in the bubble and she was rubbing his hands.
After a couple minutes of this she forced herself to pull away from him and turn herself around to face him.
"Finally you took a hint Seaweed Brain." She said with a smirk, he let out a chuckle.
"I guess I just stopped staring at you long enough to figure out you felt the same way about me"
He then pulled her close and caught her lips in a searing kiss. She put her hands in his hair while he ran his hands over her waist and lower back. When they finally had to pull away for air he said to her,
"I've loved you since I stumbled onto the big house porch and found you staring at me."
She chuckled, "Well I was too stubborn to realize it then, I realized it the next year when I was looking through your bedroom window like a pedophile."
"Well Wise Girl made a joke! What happened to you?"
"I guess you're already changing me Seaweed Brain," she replied.
He then pulled her even closer then he already had her and said, "Well I guess that means you'll be my girlfriend Wise Girl." He said excitement clear in his voice.
She wrapped her arms around his neck and placed her forehead on his, "Of course Seaweed Brain, took you long enough."
When they resurfaced an hour later they were both the happiest they'd been in a long time and they were thinking the exact same thing.
Best Underwater kiss ever.