What does WORLD RECORD marathon pace (21km/h or 13mph) look like & how long can you hold it? When filming my documentary ‘Shark vs Ross’ (AIRS NOW on @natgeotv see dates below) we tested everything and anything in the @lborouniversity laboratory 🧬 Will be posting more ‘behind the scenes’ footage on my YouTube channel (once we finish the Yukon swim film 🍿) 📣 NEW dates NEW countries added to the TV schedule: NOW on @natgeotv on @disneyplus in 🇺🇸 (USA) 🇦🇺 (Australia) and 🇳🇿 (New Zealand) (