Seek expert advice on suitable prophylaxis. There are reports of chloroquine-resistant malaria. If travelling to the interior for long periods carry drugs for treatment as these may not be available. Sleep under a mosquito net. Although there are plenty of mosquitoes on the coast, they are not malarial.
Purification is a good idea.
Tap water is usually brown and contains sediment. In the interior, use purification. In the interior, travellers should examine shower pipes, bedding, shoes and clothing for snakes and spiders. In most towns there is neither a hospital nor police. If travelling independently, you are on your own.