Natasha knew the moment she'd sent that initial message on the network that she'd made a mistake. She should've waited, talked to Steve, and approached Bucky in some other way - but now the damage was done. Knowing that he was from the 40s and had no idea who she was - or what HYDRA had done to him - led her to want to keep her distance rather than make too much of a connection. Sure, he'd be different now and she wanted to get to know him, it was still strange since they no longer had the similar backgrounds or pasts. Instead, she'd been biding her time and was waiting to approach him...and hadn't expected him to find her first.
If he'd had his Winter Soldier programming and training, Bucky likely would've noticed the fact that her pulse jumped the instant she heard his voice and her eyes landed on him, and would've probably caught the definite pause in her movements when, for just a moment, she nearly let go of the ladder. Fighting down her very physical reaction to seeing him, Natasha went instead for a polite smile as she finished climbing out of the pool and walked over to where her towel sat a few feet away.
"I remember. Good morning - you're up early. Army habit?" Natasha Romanoff could do casual with the best of them when she wanted, and sat on the edge of a deck lounger to pat her face with the towel even as she studied him, practically drinking in every detail. The last time she'd seen him in person, Natasha had been falling asleep in his arms, and she missed that on a visceral level.