I've got some real issues, with the issue of Hydration. It is vitally important to stay hydrated when we are doing things in the outdoors, everyone knows this, but most people do it wrong. I had a conversation with a friend, Beth who is a personal trainer. She has a degree in Kinesiology. She said most people should use drink additives for recovery and that you don't need an additive when you're working out - or doing whatever your outdoor pursuit is - unless you are at 80% of your max heart rate for long periods of time. Essentially endurance athletes. As my son is riding cross country on his bike - doing centuries most days, and in areas with high heat - he needs additives in his water. When I go paddling for four hours I don't. Our conversation actually started over dinner, we were talking about people at my gym, and she was saying that they are taking in calories they don't need. Water is the key. When I paddled the inside passage and I felt myself getting sluggish I used a water additive called zip fizz. It worked beautifully but I think primarily because it had caffeine in it. I am sure it was helping me hydrate as well, but the nature of a kayaking expedition means that water will work just fine.
My Astral PFD has a sleeve in the back panel that can hold a water reservoir. I stopped using it after a few days in Alaska because it only held 1.8 liters of water which simply wasn't enough. I also found it hard to fill. When I used a Lotus designs PFD there was a small backpack accessory that I used which held a bladder. It too was too small.
Which brings me to my biggest dilemma. Staying hydrated while paddling. Some people put a water bottle under their deck bungies. This works well on a day paddle, but not for extended trips. I have put reservoirs under my spray skirt, but it can be difficult to work with as the hose has to come up through the skirt. If it comes up through the bungie on the side water can get in to the cockpit. If it comes up through the tunnel on the skirt you have to deal with it every time you get out of your kayak. Think about doing a rodeo re-entry with a three liter bag of water dangling between your legs. Getting tanged in the boat while you're trying to get back into the cockpit. Water bottles under the spray skirt never work, as you can't quickly access them. When on expeditions I generally have most of my stored water in the cockpit in an MSR dromedary. This way if I need water, or have access to flowing water and can refill my water supplies I have easy access.
What I would really like is a large reservoir that lives in the cockpit directly under the deck. With a quick release port on the top of the deck in front of my cockpit. Then when I am paddling I could just click a hose into the side of my kayak and drink from the bag below the deck. I may just use a camelbak Unbottle and leave it under my deck bungies.
In terms of making water safe to drink there are many methods you can use, but first you have to understand that water can be filtered, or purified, or both.
A filter - which may be a pump or gravity fed - uses some sort of material with very small holes. The water is forced through these holes, which are big enough to let water through, but small enough to trap Giardia and Cryptosporidium - the two major causes of intestinal issues that can lead to dangerous diarrhea and then dehydration. The material itself often removes flavors and odors.
Purification uses one of a variety of methods to kill Giardia and Crypto as well as viruses. You can do it with Chemicals (chlorine based) or UV light (Steripen or Camelbak Allclear). You can also boil your water. If you bring water a rolling boil it is purified. Most pathogens are destroyed between 165º and 180º so by the time you get to 212º the water is safe to drink. Despite myths and legends about needing to boil water for ten minutes or two minutes, once it's boiling, it's done.
In Alaska we used a combination of things. We used the sawyer complete four liter system, and we used Aqua Mira. We chose which we were going to use based on whichever was more convenient at the time. Frequently we would paddle past a small waterfall, stop and fill dromedaries, add Aqua Mira, and keep paddling. By the time we got to camp the water was safe to drink.
Here is another myth - I pumped/treated my water, and the next day I had diarrhea. So the device/method I used clearly didn't work. According to the Center for Disease Control both Giardia and Cryptosporidium have an average incubation time of around seven days (though Crypto can strike as quickly as two days after infection). The methods described above are effective only if done properly. Which means waiting periods for chemicals need to be followed, and you need to be careful about the process. A big area where people make mistakes is this. You fill a bottle with water by scooping the water out of a lake or stream. You treat the water in the bottle. The contaminant is still on the mouth and threads of the bottle and you get infected anyway.
None of these processes are difficult, but you have to follow the instructions, and know the limitations of whatever system you have chosen.