Hello, I have a history of tachycardia and ectopic beats. I have had numerous episodes so have had my heart scanned which showed normal and all ecgs have shown fast but regular beat. The reason I write to you is I am very concerned after having dived into my pool and experienced a very sudden tachycardia which lasted for 5 minutes and stopped as instantly as it started. I was unable to stand and was very short of breath during the episode. This was obviously triggered by the cold water and now I am afraid of going into the pool and wondering if I should get this checked?
Chest pain and shortness of breath together with sweating very classical symptoms for abnormal heart conditions.  It sounds like when you jumped into the pool, your body went through a lot of stress due to the cold water. Therefore, it sounds like you might need a stress test in which they put your body through stress while monitoring your heart. This is one of the best tests for ischemic heart disease.  I would recommend seeing your cardiologist and letting him know about the episode in the pool. In the meantime, I would try to avoid stress.