Bella Thorne BF's V-Day Treat ... Booty & Bikinis

2/15/2016 9:15 AM PST BY TMZ STAFF

0215_bella_thorne_bikini_mexico_launchBella Thorne did her Valentine's Day duty for BF Gregg Sulkin -- and her gift was way better than some flowers or chocolate.

The couple celebrated at the Hard Rock Hotel Riviera Maya with daiquiris and, most importantly, some serious PDA in the ocean.

The 18-year-old Disney star looks pretty serious about the relationship -- booze (she's legal in Mexico) and a beach vacay will do that.

At least it got Bella into an itsy bitsy teenie weenie polka dot bikini. So, we all win.