Bleeding part 2

Serious bleeding falls into two categories: arterial bleeding and venous bleeding. Arterial bleeding involves an injury to a vessel leading from the heart. Arteries carry oxygen blood, characterized by being bright red. You may also tell arterial bleeding by a spurting wound. Venous bleeding involves injury to a vessel leading from the body tissues. Veins carry deoxygenated blood, characterized by being a dark red. Venous wounds tend to bleed steadily. In a severe wound, you can have both arterial and venous bleeding at once.

Note that wounds underwater may not bleed red at all. In water shallower than approximately 10 metres/30 feet’s, blood looks brownish; deeper than that, it looks green. A greenish cloud coming from your buddy's hand, for example, more than likely mean he just cut it severely.