Serena Williams: Best mASSage Ever

Here's Serena Williams getting a sports massage in a one-piece bathing suit and we assure you it's EXACTLY what you need to get through the rest of your work day.

The short vid went up on SW's Snapchat moments ago ... and while it doesn't quite live up to the bootyful star-spangled outfit she wore on Snap some months back -- we assure you of one thing:

You won't be disappointed.

So watch ... and check out Serena's devilish grin. She knows what she's doing.