This question depends on the person. Usually by around 200 to 210, your heart begins to go into an abnormal rhythm or disrythmia, called VT or PVT. The respectively, stand for Ventricular Tachycardia and Pulseless Ventricular Tachycardia (PVT is the more dangerous variety). At around this stage a patient runs the risk of cardiac arrest, which is dangerous because while the heart continues to beat, the contractions are so fast, blood isn't being let into the chambers of the heart. Without blood actually being pumped, the person is unable to perfuse, and goes into shock, seizure, coma, and then death.
The correct answer should be low to moderate intensity and long duration. For weight loss, it's better to do something at a lower intensity but for a long time than to do something quickly but pushing yourself. That's why cardio exercises and running is great for losing weight. It helps you work at your own pace and you can do them for a long time.
I'm pretty sure I that it depends on the tide of the water. When it's low tide you can go deeper in the water when it's high tide you can't go that far without touching the ground
Accidents are unfortunate events that happened unintentionally, while risky behaviors usually intentional even though the negative effects are already known.
One example of accidents is if plane passengers died during the plane crash. And the example of a risky behavior is to use tobacco product despite the negative effects it has on health.
