The first time Renée O’Connor appeared on camera in a swimsuit (near as I can tell) was in the Disney serial MATCH POINT in 1989.
Renee O'Connor in bikini in 1989's MATCH POINT
The next swimsuit appeared in Danielle Steele’s CHANGES.
O'Connor in inner tube and industrial strength swimsuit in CHANGES (1991)
Then there was the docudrama THE FLOOD: WHO WILL SAVE OUR CHILDREN in 1993.
O'Connor in red swimsuit in THE FLOOD
Rockford Files’ 1996 TV movie A BLESSING IN DISGUISE had O’Connor’s character Laura Sue Dean watching herself wearing a bikini in a TV commercial for a product called Sports Quencher.
O'Connor is second from left in this shot from the TV ad within the Rockford Files film A BLESSING IN DISGUISE. Identitles of the other three in the photo are unknown.
There weren’t really swimsuits in ancient Greece. The closest thing Gabrielle ever wore to a swimsuit was this interesting item in the Season Five strangeness MARRIED WITH FISHSTICKS.
Gabrielle at the pool in MARRIED WITH FISHSTICKS
And recently, 2010:MOBY DICK begins with O’Connor in a bikini (under a pair of shorts) searching for whale song from her boat The Coffin.
O'Connor in 2010:MOBY DICK