After my partner transitioned, I was surprised she wore a bikini on a family trip. I learned so much about her that day.

• After 11 years together, my husband came out as trans and is now my wife.
• Her choice of bathing suit on a recent vacation surprised me — and helped me understand her better.

Sometimes I momentarily forget that my husband has transitioned and is now my wife, Stefanie. So when a neon-pink bikini appeared in a family suitcase crammed with toys and diapers, I thought: Whose bathing suit is that?

I blinked, bleary from traveling from New York to our beach vacation in Provincetown, Massachusetts. We were there for Family Week, the largest gathering of LGBTQ families in the world. As I tucked the silky pink straps into the dresser drawer, I wrestled with a range of feelings about the bathing suit: admiration, ambivalence, maybe a little jealousy.

Should I be wearing something pink and fun too? I'm a middle-aged mom of two, and I feel my bikini days are long behind me.

My wife's transition has been joyful and mind-bending for the family. At times it's confusing for me, as a cisgender woman, to see the person who was very recently my husband become more of a girly girl than I am.

My wife wanted to show off her new body at the beach

Stefanie lost 85 pounds during her transition through daily running, intermittent fasting, and a new vegetarian diet. After a lifetime of feeling ashamed or dissatisfied with a body that didn't match her gender identity, she wanted to celebrate herself on the beach. I'd never thought of a bikini as a radical feminist expression before, but on my wife, it definitely is.

Since my teens, I'd thought of bikinis only in terms of the male gaze and the way they're used to objectify women. I'd never thought of a sexy bathing suit as something that empowered the person wearing it. Since my teens, I've worn a series of black racing Speedos, because I didn't want any attention. I don't go to the beach to be on display — I go to swim. I need a bathing suit that helps me fly.

I also want our two daughters, 10 and 3, to embrace the beach without being self-conscious about their bodies. I've always steered my girls away from cutesy, frilly two-pieces. We all wear shorts and rash guards so we're comfortable and protected from the sun.

The first day Stefanie put on her pink bikini top with her swim shorts, I complimented her appearance. "But I was pretty surprised!" I admitted.

Stefanie gave me a wistful smile. "I've always wanted to wear a bikini."

I learned something new about my wife

Throughout our 12 years of marriage, I'd had absolutely no idea. A door opened to my wife's past, and I gained a new understanding of her.

Growing up in Southern California, she gazed at surfer girls in pictures with a sharp longing that wasn't just attraction. She also wanted to be a surfer girl — carefree, sun-dappled, frolicking in the water. After transitioning at 43, she realized it wasn't too late to live that dream.

I had a childhood ocean fantasy, too: I wanted to be a scuba diver. That must be why rash guards give me a feeling of exhilaration. After reflecting on this with my wife, I found a new sense of peace with my prudish style.

Stefanie and I want to show our daughters that there are many ways to express femininity — and countless ways to feel beautiful. A bathing suit seems like a trivial thing, but these everyday choices make us who we are. I hope that when my daughters go to the beach throughout their lives, they'll find their own ways to soar.

Jess deCourcy Hinds is a writer in Queens, New York. Her free quarterly newsletter is I'm an Open Book: On Love, Libraries and Life-Building.