I am standing on the beach, ready to live out my lifelong Gidget fantasy.

When I was 11 years old, I had a dream. It was a flight of fancy shared by every starry-eyed, landlocked, adolescent lass in mid-’60s America.

I wanted to be a surfer girl.

My obsession was due, in large part, to Sally Field, who played the irrepressible “Gidget” on TV. (Yes, all you Gidget purists, I know Sandra Dee was the original surfing pixie, but I was barely out of diapers when the movie came out. Sally Field will always be Gidget to me. It was, in my mind, her greatest role, “Norma Rae” notwithstanding.)

Gidget was pert and petite. She wore a yellow ruffled bikini that covered her navel, and all the boys adored her. “Gidge” was smart and sassy. She was sweet to her widowed dad and loyal to best friend, Larue. She had a princess phone and a boyfriend in college. Princeton, no less.

And – cowabunga! – could that girl surf. With giant waves crashing behind her (I was blissfully unaware of green screen technology back then), Gidget could easily hang 10 with Moondoggie and all the guys.

I didn’t want to be just any surfer girl. I wanted to be Sally Field.

Each week, after watching an episode of “Gidget,” I would dash up to my room, turn on Jan and Dean, jump onto my bed and “surf” the wild “waves” of my springy mattress. I’d bend and sway and – whoa! – almost fall off my “board” to spin my arms, windmill-like, to save myself from a wipeout. I was convinced I could shoot the curl. If only I could find waves bigger than the ones in my bathtub.

Forty years later, standing on a beach in Sayulita, Mexico, I finally have my chance. Located 35 miles north of Puerto Vallarta, Sayulita is reportedly one of the best places for beginners to learn how to surf. It’s also a great spot for experienced surfers to do some hot-dogging. Something about the beach having a right and left break, whatever that means.

I’ve been watching people lug their surfboards past my umbrella all day. Tan, muscular types – men and women – carrying long boards on their heads or short boards under their arms.

I observe them for a while longer, then realize the common denominator they share: They are all under 35 years of age.

A chorus of alarm bells goes off in my head. Maybe surfing isn’t something I should rush into.

Instead, I grab the boogie board that came with our rental villa and, with the Beach Boys’ “Catch a Wave” playing in my head, I bound for the water.

“If I pass the boogie board test,” I think, “I can advance to real surfing. I’ve been boogeying since the ’70s. How hard can it be?”

I skip into the ocean, cold waves lapping at my legs. I wade out, deeper and deeper, until the water is chest-high. Off in the distance, a swell is building and heading toward me. It looks big.

I’m stoked!

“Surf’s up!” I cry and hoist myself onto the board, hugging it and bracing for the ride of my life.

The wave starts to curl downward. It’s a FREAKING TSUNAMI! I start to kick my legs and paddle furiously to get out in front of it.

Before I can cry “Banzai!” the wave crashes down, pitching me forward in a gnarly whirl of blinding, salty foam. The board flies out from under me and, after a two-second head-over-heels tumble, I land facedown on the beach. My hair completely covers my face. My swimsuit is twisted into a wad, and I’m swallowing sand.

Something tells me I didn’t exactly rip it.

Just then, I experience another of life’s revelations.

Sally Field isn’t surfing anymore, if she ever did at all. She’s shilling for Boniva, for crying out loud. “Gidge” is a spokesperson for osteoporosis medication!

Dude. Talk about a wake-up call.

I rescue my boogie board from the drink and head up to the villa. I inform the family I’ll be in my room.

As I traipse through the sand, the tune in my brain changes to the melancholy strains of “Surfer Girl,” and I start to smile.

I wonder if my mattress breaks left or right.