Nope.

Floating on her back while allowing the relatively calm waves to rock her back and forth, Yang was completely oblivious to the fact that she was currently naked. All it would take was a single glance down and she'd see the exposed mounds of soft flesh that were her breasts. However the blonde was content to simply laze about in the water while she waited for Ruby to return.

Fortunately (or unfortunately, depending on perspective) Ruby eventually made her way back into the water while carrying a massive beach ball above her head.

"Yang! I'm back!" the younger sibling called out as she approached her sister. "I got us... a... big..." Ruby trailed off as she noticed Yang's current state of dress, or rather lack thereof.

Perking up, Yang righted her posture so that her front was completely facing Ruby. "Alright! Time to have some fun!" she cheered, still unaware of her nudity. Although she did tilt her head in confusion when she noticed the strained expression Ruby had on her face. "Something wrong Rubes?"

Ruby was well aware that her sister could be oblivious at times, but she had no idea that it could get this bad. Unless she was naked on purpose? The reaper shook her head. She didn't recall Yang being into exhibitionism. The warning that Yang was naked was on the tip of her tongue, but she paused just before speaking as she thought back on all the pranks Yang had pulled on her over the years. The more devious part of Ruby's mind saw this as the perfect opportunity for some much needed payback, while the more reasonable side reminded her that Yang's **** would be merciless if she realized that Ruby pulled one over on her.