With the average age of the diving community steadily increasing, the prevalence of (often undetected) cardiovascular disease is also on the rise. It is understood, that cardiac disease is associated with 20-30% of fatalities amongst recreational divers. Immersion alone triggers a variety of physiological responses, which might be augmented by other factors like cold, hyperoxia, or hypercapnia to name but a few. In this lecture, we aim to break down the complex effects of diving and extreme exposures on cardiovascular function and look into some recent studies on the matter. We will also present data of DAN study about prevalence of possible risk factors for sudden cardiac death, arrhythmias and structural changes in heart anatomy in over 80 recreational and technical divers.