n the dry season, when the rivers become shallower, in their most shallow part they are quite calm, but from the middle part of the river and downstream from it, the current tends to be quite strong. In these areas there are strong whirl pools, locally known as "moyunas" that can drag you down into the deep.
Before crossing a river, observe its shape, check if it is a large lake or a so called cocha with quiet waters, it is important to see if it has calm waters without a current. If this should be the case you must be careful because there might be carnivorous piranhas in there.
Piranhas can be found in any place in the Rain Forest where there are calm waters in the river. They can generally be found where there are clam rivers, lakes or cochas and in big swamps. Many of them are carnivorous fish and can be attracted by the smell of blood in the water, so if you have a recent wound that is bleeding, do not enter the water and try to find some dry balsa wood logs or similar to make a raft in order to cross safely. In the same waters that you can find the piranhas there are usually also a kind of small cylindrical shaped fish locally known as “carneros”, which close to their head have two fins in the shape of the barbs of an arrow point.
These fish usually bite the people that try to cross the river and twisting and turning around they are able to rip off a piece of meat, making the person bleed, all of which may provoke the piranhas to attack. If the river runs fast and has a strong current, then the best thing you can do is not to encounter this kind of fish.
If you plan to enter a river, take off your shoes or rubber boots because they may fill up with water and make it impossible to take them off since they will be filled with water and too heavy to take off easily. Once in the water it is almost impossible to take them off since they will form a vacuum.
If you do not know how to swim and even if you do, the safest thing to do if you want to cross a river is to make a raft or to find one or several balsa wood trunks or some other wood that floats easily in order to use them as a kind of life saver, before using them, make sure the trunk will float because many of the Rain Forest hardwoods will sink in water. And before crossing, try to find a place where there is not a strong current.
Do not try to cross a river during a thunderstorm with lightning or if it seems that one is coming, because you might have a bolt of lightning strike close to you and it could electrocute you if you are as close as 600 metres around from where it strikes. This danger is multiplied by several factors if it is raining at that moment. If a thunderstorm with lightning surprises you when you already are on the river, get close to the banks and take shelter beneath the riverside low vegetation as soon as possible. Stay there until the storm blows over.
If you have to cross the river by swimming, please heed the following advice:
a) Swim on your back or using breast strokes, since it will tire you out less.
b) Only start swimming when the water reaches your chest.
c) In very deep or rivers with a fast flowing current, cross diagonally in favour of the current.
d) In rivers with fast flowing currents swim on your back with your feet facing down stream, your body in a horizontal position and your hand close to your body as if they were fins.
e) Try to stay away from the confluence of several currents because there you will find the formation of the so called "moyunas" or whirl pools.
If you cannot swim, improvise floating cushions using tree trunks tied together with ropes. Always check that the trunks will float before taking the risk of getting into the water. Look for wood of Pona Palm Trees or Balsa Wood or the so called Cetico Tree, which are the ones that float the best.