Condoms are great. They keep stuff afloat (as I have already mentioned), they keep stuff dry (like firearms or electronics - neither like being submerged), they can be used to get drinking water (the old stick it over a leafy branch trick), they can be used to contain liquids (drinking water). They can be used as the elastic in a spring trap for small animals, or to cover wounds (such as weeping blisters on feet - not optimal, but better than foot rot). And they can protect you from STD/Is, as well as an unwanted pregnancy.