Stephanie Montero Bending - Bahía de Banderas

Islas Marietas to Las Gemelas

36.2 km (22.5 miles)

14 hours, 30 minutes on 18-19 November 2023

Observed and documented by Karina Yazmín Almanza Hernández




Support Personnel


Karina Yazmín Almanza Hernández

Observer on 55kms swim attempt in El Reto Acapulco, Mexico in 2023. Crew on several English Channel solo swims and Reto Acapulco swims. YMCA aquatic safety course in 2023.

Escort Vessels

Swim Parameters

  • Category: Solo, nonstop, unassisted.
  • Rules: MSF Rules of Marathon Swimming, without exception or modification.
  • Equipment used: Textile swimsuit (Arena training suit), latex cap, Speedo goggles, grease.

Route Definition

  • Body of Water: Bahía de Banderas, Pacific Ocean
  • Route Type: one-way
  • Start Location: Northeast corner of Isla Larga, Islas Marietas (20.700700, -105.580234)
  • Finish Location: Las Gemelas beach (20.549650, -105.272244)
  • Minimum Route Distance: 36.2 km (22.5 miles) (map)


First known swim of this route. Previously in October 2021 there was a swim in Bahía de Banderas, with different start and finish points. It was from Punta Mita to Cabo Chimo, covering 32kms.

Swim Data

  • Start: 18 November 2023, 17:29:11 (America/Mexico_City, UTC-6).
  • Finish: 19 November 2023, 08:00:10
  • Elapsed: 14 hours, 30 minutes, 59 seconds.

Summary of Conditions

Feature Min Max
Water Temp (C) 29 29.5
Air Temp (C) 25 29
Wind (knots) 4 11

GPS Track

Trackpoint frequency: 20 minutes. Download raw data (CSV).

Click to expand map.

Speed Plot


Observer Log

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Swimmer Statement

Cruce de Bahía de Banderas, a swim in aid of the conservation of the humpback whale
The adventure of my life.

By Stephanie Montero

The challenge: to swim across Bahía de Banderas Bay in Mexico, one of the largest and most beautiful bays in the world, at night. Starting in Islas Marietas National Park, a protected natural area in the state of Nayarit, passing near Los Arcos, a natural area that needs protecting, and finishing at Las Gemelas beach in the state of Jalisco. The crossing is not a straight line because it includes the pass near Los Arcos, but it was key for me to draw attention to this natural wonder.

My aim: to raise money ($30,000 USD) for an NGO ( and encourage collaboration among multiple sectors in order to support the conservation of the humpback whale, which faces serious threats on its annual journey back home to Bahía de Banderas, such as entanglement in fishing gear, ship strikes, plastic pollution and climate change.

The start of the swim – My dream becoming reality. November 18th, 2023. We embarked in Punta de Mita and the Marathon Swimmers Federation Rules were read out. We set off for Islas Marietas amidst jokes and laughter, marvelling at the sea and the islands, under a clear blue sky. My team helped me get ready for the swim and I jumped into the water. I swam to the Escalones de Piedra beach in Isla Larga in a state of complete bliss and full gratitude, with no hurry to start. The beach is small and cosy, with a view of its sister island, Isla Redonda, and a rocky arch through which you can see an islet in the background.

The team was ready, and I was ready, ready to enjoy every stroke and give everything I had. I felt strong and confident, I felt safe with my team by my side, I felt loved by my family and friends, and I felt supported by lots of people, many of which I didn’t know. I needed nothing else. I raised my hand and I walked into the sea, my happy place.

The sea embraced me, the water temperature was perfect; I swam over coral reefs, with curious fish underneath me. I got into a good pace, Islas Marietas were getting smaller and smaller behind me, they looked beautiful because of how the sunlight struck them. After an hour or so I stopped to enjoy the beautiful sunset with my team and I waved goodbye to the sun. At the same time the moon was already shining high up in the sky.

A magical night. It gradually became dark. Afraid? Not at all. Swimming in the ocean at night is magical. The stars began to appear. Although cloudy most of the night, the moon would peek out from time to time and smile at me. Some waves carried me forward and I just flowed with them. The bioluminescence accompanied me all the way, it was as if I were creating stars with every stroke.

At some point I started to feel tired, especially my shoulders. As if by magic, a thin layer of icy water suddenly appeared on the surface of the ocean, followed by refreshing rain that helped me ease that aching feeling and tiredness. Although I didn’t see them, except for one near Los Arcos, I got stung by at least 10 jellyfish and many sea lice during the swim. It hurts at first, but the pain quickly goes away.

The wall. I was making great progress until I realized I was moving little or not at all by looking at a triangle of lights in the horizon, which remained the same size for a long while. I had encountered a strong current, which I came to think of as “the wall”. I barely remembered Amilcar´s forecast (the oceanographer) but I recalled him mentioning there was going to be a strong current or wind until 9 am, and I thought “if this is why I’m stuck here, I’ll be swimming in the same spot for at least four hours”. After a few minutes of despair wondering if I would finish the swim, I controlled that thought by accepting the possibility of swimming until 9 am. I slowed down, I stopped looking at the lights, I started counting my strokes, and I went into a state of deep meditation. Because of this, I almost crashed into the boat, my team shone the lamp on me to warn me and I reacted just in time.

Los Arcos, my favourite place in Bahía de Banderas. After a while, I felt I was moving forward again. It was getting brighter as dawn approached and I was able to see Los Arcos on the horizon. I cried, I felt so much joy and relief because I knew I was close to the finish line. As we turned towards Las Gemelas beach where I was going to land, a small pilot fish suddenly appeared in front of me and accompanied me until the end, a wonderful gift!

I dreamed of it and I made it. I was almost there. My team were cheering me on and I could see my family and friends in the distance, I increased my pace. I touched land taking care not to lose my balance when I stood up. My feet were out of the water; I turned, raised my hand, and heard the whistle. I burst into tears. My family and friends hugged me and we cried; I was living a dream, the dream of my life! I cried of happiness; I had achieved everything I had worked so hard for. I returned to the water and swam back to the boats. My team jumped into the water, I hugged each one of them and thanked them. Back on the boat on our way to La Marina, a humpback whale and its calf appeared, I could not have asked for more.

My team, the best of the best. They did not lose sight of me for a minute. Alex Arévalo (kayaker) often smiled at me, Coco Villegas gave me thumbs up, and the rest of my team didn’t stop cheering me on for the whole swim. They provided everything I needed including food and beverages but, most importantly, they gave me their hearts, they cared for me, they enjoyed the swim and they made me laugh. I am forever grateful, open water swimming is definitely a team sport.

Key accomplishments

  • We raised +40,000 USD and increased awareness of at least 1000 people in Mexico and in several countries around the world, mainly by organizing the First Swim for Whales 2023. This project would not have been possible without Karina Almanza, Yoselin Gloria, and Maricarmen.
  • More than 60 organisations from government, civil society, academia, the private sector and the media supported the cause.
  • I achieved the crossing – 37.5 km in 14.5 hours. It was the adventure of a lifetime, I savoured every stroke and every minute in the sea, I became one with the ocean. I feel very fortunate to have lived this amazing experience and to have been able to give something back to this beautiful world.

Many thanks to my friends and family, to my team, to all the sponsors for trusting and supporting me from the beginning and to each person that was sending good vibes during the swim.

Special thanks to Trudy Ederle, Mercedes Gleitz and Lynn Cox, my role models, for their inspiring stories.

“I know no sensation but that of calm pleasure of the prospect of another tussle with those, calling, waves. When one loves, one is not afraid.” Mercedes Gleitz.


Click to enlarge.