Lindsay Lohan's Beach Birthday Celebration Begins Early in Greece

Lindsay Lohan's getting the party started a little early for her birthday ... hitting the beach at one of her favorite spots in Greece.

The soon-to-be 31-year-old arrived in Mykonos Thursday and enjoyed a boat ride and a refreshing dip in the sea. Even though the celebration has begun, her bday's not actually until Sunday.

What's interesting -- Lindsay's rocking a green emerald ring ... very similar to her old engagement ring. Don't be fooled, though -- we're told she just loves emeralds, and it's actually part of her new jewelry line ... aptly called Lohan by Lindsay Lohan.

Happy early birthday, Whatsyourname!