Thank you Tom for your answer !
Next time I will follow your advice, I was so excited by doing this, so I think I needed to experiment the hustle fear.
Thinking about my stroke it is something I tried to focus on ,when you swam in open water you have a different feelings it s definitively less boring and more relaxing than the pool. 1k is a small competition i will do another one soon but I think I can go for a longest distance now after 1300 meters I felt no exhaustion at all. It became very natural to breath on both side without any discomfort which is for me one of the best gift Terry share to me.
So you are right, Iím thinking about buying a swim buoy....