There is comparatively little canoeing done in Namibia, though operations do run on the country's borders: down the Orange River, on the eastern side of the Kunene, and occasionally on the Kwando, the Chobe and the Zambezi. The main dangers for canoeists are:
Hippos are strictly vegetarians, and will only attack a canoe if they feel threatened. The technique for avoiding hippo problems is first of all to let them know that you are there. Bang your paddle on the side of the canoe a few times (most novice canoeists will do this constantly anyhow).
During the day, hippopotami congregate in the deeper areas of the river. The odd ones in shallow water, where they feel less secure, will head for the deeper places as soon as they are aware of a nearby canoe. Avoiding hippos then becomes a simple case of steering around the deeper areas. This is where experience and knowing the river become useful.
Trouble starts when canoes inadvertently stray over a pod of hippos, or when a canoe cuts a hippo off from its path of retreat. Either situation is dangerous, as hippos will overturn canoes without a second thought, biting them and their occupants.
Crocodiles may have sharp teeth and look prehistoric, but are of little danger to a canoeist... unless you are in the water. Then the more you struggle and the more waves you create, the more you will attract their unwelcome attentions. They become a major threat when canoes are overturned by hippos – making it essential to get out of the water as soon as possible, either into another canoe or on to the bank.
When a crocodile attacks an animal, it will try to disable it. It does this by getting a firm, biting grip, submerging, and performing a long, fast barrel-roll. This disorients the prey, drowns it, and probably twists off the bitten limb. In this dire situation, your best line of defence is to stab the reptile in its eyes with anything sharp that you have. Alternatively, if you can lift up its tongue and let the water into its lungs whilst it is underwater, then a crocodile will start to drown and will release its prey.
There is one very reliable report of a man surviving an attack in the Zambezi. The crocodile first grabbed his arm and started to spin backwards into deep water. The man wrapped his legs around the crocodile, to spin with it and avoid having his arm twisted off. As it spun, he tried to poke his thumb into its eyes, but this had no effect. Finally he put his free arm into the crocodile's mouth, and opened up the beast's throat. This worked. The crocodile left him and he survived with only a damaged arm. Understandably, anecdotes about tried and tested methods of escape are rare.