If you honestly thought it was the truth, and later found out it wasn't, then you were not really lying.
As for swearing to God.. things like "I swear to God" and "God damn" etc have become common sayings in society. People say them without really giving any thought to them.. they are not...
I think it's totally fine. I enjoy going to the beach with my friends and having a great time every summer. I don't wear bikini though, because I'm persoanlly not comfortable with it, but I don't see a problem if someone is.
Welcome to CF. I hope you'll enjoy it here. We have quite a few active Buddhist members, mostly seen in the non-Christian religion section. I hope to see you around the forums. ^_^