When I was young, Dad used to talk to us about Mars on the beach. He would lay out his big AC/DC towel while Mom rubbed us down with sunblock and warned about the dangers of sunburns and skin cancer. While my brother and I made drippy sandcastles, Dad described rust-colored mountains and endless red deserts. At the time, I didn’t understand the significance of what he told us. Mars never seemed like a place I’d ever see, and building a colony on another planet sounded make-believe. I didn’t think that we’d actually leave. All I wanted was to swim for sand dollars.

We lived in a small town on the western coast of Florida. Thoughts about space or Mars or anywhere else didn’t cross my mind much. Life by the beach was all I knew and all I needed. My brother and I would buy ice cream cones at the corner store and patrol the beach for sea glass and corals to add to our collection. Hyped on sugar, we’d lay them out on my dad’s AC/DC towel and pick through our findings day after day. We’d do this all year—each year more shells, fish bones, and corals washing on our beach. At night I’d hold starfish to the sky and wonder what glowing speck was Mars.

I never shared my dad’s fascination with Mars. My brother sometimes got caught up in his stories, but I was never swayed. Mars didn’t have fish, or dolphins, or corals, or sand dollars. It was a boring red desert with a single metal base. No one snorkeled or boogie-boarded on Mars, and I couldn’t go to the corner store to buy ice cream on its rusty mountains.

At seventeen, my dad had been on Mars for nearly two years. Besides for our monthly video calls, we had little contact with him. He kept us informed of the progress on his Mars base, and we filled him in on what he missed at home. Without Dad, Mom spent most of her time inside while I went out to the beach every day. My brother liked to keep Mom company, something I was always grateful for. Dad used to love coming to the beach so I made it my duty to show him my findings every time we got to talk. I was surprised to see the worry on his face when I showed him the skull of a dolphin I had found.

That was when I realized we really were going to Mars. Yes, my whole life my dad had been telling us that we’d move to the big red planet one day, but it always felt more like bedtime story. Like when someone says they want to see Japan or Australia but everyone knows it will never really happen. This time though, it felt different. I knew that we wouldn’t be able to stay in Florida forever.

I left that video call as if walking through a bad dream. The oceans were dying. The planet was dying. And we were moving to Mars in less than a year. I left the house after Mom started dinner and walked to the beach in a daze. My mind was crowded with the difficult idea of leaving home. The beach was my life. I hoped walking to it would calm me as it always did. But, as if opening my eyes for the first time, I noticed the changes that I had ignored.

It wasn’t as if I was oblivious to the changes. I had just thought about them in a way that was easy to imagine. The water was no longer warm and colorful but thick and foggy. The shore wasn’t covered in treasures and sea glass but covered in litter and carcasses. The fish I had been swimming after just the other day were suddenly starved, frail, and sick instead of slow and stupid. The corals were bleached and brittle instead of bright white and easy to collect. The burning sun, which had been so warm and friendly, now set over the ocean, its orange intensity reminding me of an oil fire.

Two days later, my mother told me to stay away from the ocean.

After I was barred from the ocean, reality hit me. After we moved, I’d never get to see the ocean again—any ocean. I’d never swim after snappers, uncover sand dollars, or watch dolphins flip over the waves. I could never taste sea salt or feel the wet sand or hear the waves or the wailing gulls. There was no natural water on Mars, and even though Dad bragged about the artificial lakes NASA had established, the thought of it sunk in my chest. There were no corals, fish, dolphins, or whales in those filtered bathtubs. Would we sit on concrete benches and sift through plastic shells and aquarium corrals? Would we coat ourselves with fake sunscreen to protect ourselves from a giant light bulb in the ceiling?

I tried to sneak back to the water during our final summer. I had to see the ocean one more time. Our house was sweltering, and Mom fixated on the news that cycled reports of burning forests, flooding coasts, and widespread famine, watching these stories on repeat all day and night. It was depressing to stay indoors, but outside wasn’t much better. The ocean had risen far past the old beach. Instead of white sand, cracked asphalt roads and muddy flats dropped off into thick soupy water that lapped against the broken shore, visible from my bedroom window. Soon, that water would be our doorstep.

The night before we were meant to leave, I decided to take a final swim despite the dangers. If we were going to Mars, this would be my last chance. Oceans would be a thing of stories and legends soon. While my mom and brother packed the last of our things, I slipped out the back and made the short walk to the shoreline, which was now half a block past the old corner store.

It was late afternoon, and the red sun was setting over the dying ocean. Clumps of flotsam dotted what had once been streets and stores and homes. I squinted and pretended that the trash was dolphins or sharks skimming the water as they used to years ago. Against my mother’s warnings, I dipped a toe into the water and held it there. The water was hot. Not warm, but hot like a bathtub. It felt slippery like spoiled milk.

I followed the shore out of town to the closest remnant of a beach I could find. It was a small strip of gravel and mud carved out of a hillock near an old water tower I never thought about. I rolled out my dad’s AC/DC towel, placed down glass, corals, and shells, and sifted through them, pretending as if nothing had changed. I imagined the waves behind me crashing on rocks and sandbars, not brick walls and broken fences. I picked through my ocean treasures until the stars came out, and I did everything I could to keep from looking at them. I tried to focus on my small world outlined on that towel, far below the stars and that single red planet.

I sat until hightide hissed at my feet. Then, I packed my things and left forever.