Jari's longest unsupported swim

Swedish adventurer’s second attempt at world’s longest unsupported swim

This summer, Swedish adventurer Jari Cennet Tammi is planning his second attempt at the world’s longest unsupported swim – from Stockholm to Helsinki across the Baltic Sea

This summer 64-year-old Swedish adventurer Jari Cennet Tammi is planning a record attempt at the world’s longest unsupported swim.

On 10 June 2023, Jari will embark on his challenge to swim from Stockholm in Sweden to Helsinki in Finland. The distance of the swim is 500km, which he plans to complete, unsupported, over 37 days. He will be towing a kayak containing his food and gear.

This is Jari’s second attempt at the world record. Last summer he had to abandon the swim after 180km, when wind changes would have caused him to miss the island of Lågskärfyr, a landmass that’s only 1500m long. Missing this island would have meant no other land in sight within 50km.

With this setback in mind, Jari will only swim this section of the route when there’s a westerly wind to keep him on track for the island.

It’s just a couple of months until his challenge, so we thought we’d pull Jari away from his rigorous training (including towing four filled 5L canisters while swimming!) to find out more about his daring feat.

Jari, it’s not long until your second attempt at the world’s longest unsupported swim. How are you feeling?

I can’t wait to start, and to be part of a new adventure out among islands, skerries and the open sea, in my solitude.

How have you been training for the challenge?

I swam a lot in October and November using the Tri Swim Speed 3.0. This tandem device allows you to train with a slower swimmer in the open water. You get a good workout with more resistance.

Recently I’ve been swimming with my Ruckraft weighted with 6kg cargo, plus four filled 5L canisters, which I tow behind me. This simulates the weight of the kayak I’ll be towing.

What are the difficulties of swimming in this part of the Baltic Sea?

In Stockholm’s archipelago, navigation is a big challenge because there are over 30,000 islands. When you’re in the water, they all look the same!

Small boat traffic will also be a problem in the archipelago because boaters will not expect to encounter anyone swimming.

In the Åland Sea, there’ll be lots of cruise ships and cargo ships passing.

What could go wrong?

In the Åland Sea I’ll be swimming 30km of open water. I’ll need a westerly wind to hit Lågskär, an island that’s only 1500m long. If the wind changes from west to north or south, I’ll drift off course and miss the island. This is exactly what happened last summer.

I’ll have 37 days’ worth of food. If I’m delayed on Söderarm (the start of my Åland Sea swim) because of strong winds, my food supply will decrease every day. If this happens, I’ll have to ration my food later.

What conditions are you hoping for?

I wish for a westerly wind of 5 meters per second, and of course sunshine during the day and cloudless at night. I start at 2pm, and if everything goes according to plan I will see Lågskär’s lighthouse in the dark, guiding me towards the island.

How have you prepared yourself mentally?

In summer 2021 I swam solo for 328km in 32 days in Stockholm’s outer archipelago. This and my attempt of the Stockholm to Helsinki challenge last year is how I’ve prepared myself.

Are there any key items of kit that will aid you during your swim?

For navigation I’ll be using the Marlin Swim Meter GPS. With this I’ll get direction, speed, distance and total time communicated through a small speaker on my temple as I swim.

For my drinking water I’ll be using a Katadyn Survivor 35 – an emergency desalinator that can produce 4.5 litres of water per hour. It operates manually with no electricity required.

I’ll also be taking a steel Landsort diver’s watch recently launched by Sjöö & Sandström. The watch will be auctioned off to the highest bidder after my swim, with proceeds going to Baltic Waters 2030, a foundation that works for a brighter future for the Baltic Sea.

We’ll catch up with Jari again after his challenge in June. You’ll be able to track Jari’s journey in real-time via a link to his GPS tracker, which he’ll post on his Facebook page.

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Abi writes swimming news stories and features for the Outdoor Swimmer website and manages the social media channels. She loves to swim, run, hike and SUP close to her home in Herefordshire. While she’s a keen wild swimmer, Abi is new to the world of open water events and recently completed her first open water mile. She has previously written for The Guardian, BBC Countryfile Magazine, BBC History Magazine and Ernest Journal.