How to Survive a Piranha Feeding Frenzy

How to Survive a Piranha Feeding Frenzy

It's a hot, dry day in July when you decide to explore the Amazon basin by boat. You feel pretty comfortable with your local guide showing you the exotic environment. But all of a sudden, your boat capsizes and you fall overboard into the still, warm water. Luckily, you're a strong swimmer. Wait a minute. What are all those fishes? And why are they
swarming?