The Encyclopedia of Earth says that “We live on a planet that is dominated by water. More than 70% of the Earth’s surface is covered with this simple molecule.” Scientists estimate that the hydrosphere contains about 1.36 billion cubic kilometers of water and most of it occupies topographic depressions in liquid form.”
On any trip, millions of water molecules are trying to find their way into your phone, your camera, your lunch, and onto your map and towel. Kayak manufacturers have made many attempts to create 100% waterproof compartments in their boats but so far they have been largely unsuccessful.
With necessity being the mother of invention, many containers, cases, and bags have been developed as solutions to the problem. It is a good idea to use a combination of these in various sizes rather than just one big one. This is because each time you open a bag to retrieve a particular item the remaining gear inside is exposed.
KEYS: A one litre dry bag works well. Some people use a plastic jar, like a peanut butter jar. Just make sure that it’s watertight. Naturally glass jars are not a good idea. Oh, and try to eat all the peanut butter first.
PHONE: There are several cases that are sized specifically for phones and have at least one clear side so you can make and receive calls without having to open the case.
MAPS: It is possible to get waterproof map cases that are clear on both sides so you can see your maps and guides while you are in the boat without worrying about them getting ruined.
TOWEL AND FOOD: These can often be combined in the same dry bag because you usually get them out at the same time. The size of bag required will depend on your towel. If you have a microfibre towel, ten litres might be enough. Otherwise, you might need up to twenty litres.
FIRST AID KIT AND SPARE CLOTHES: As emergency items, these should be kept in their own ten to twenty litre dry bag.