Life jackets are indeed saviours in the unforgivable water. If you think they are expensive, you could search online or at stores for life jackets for sale but you should never compromise on quality.
Just like the name suggests, life jackets should be worn in order to be safe in water. They have been designed to protect you and to save your life from drowning. These are your only line of defense when in the water. They protect you in many ways and some of them are listed below along with some information:
Type III life jackes provide US Coast Guard compliant flotation to keep your head out of the water, but do not have the head pillow. Whitewater rafting requires Type II (life vest design with head pillow).