When water is shallow enough, wading is a very effective way to reach a victim. Wading also enables a team to safely transport a victim with far more control than swimming.
In a number of rescue scenarios, it may be necessary to get a person at the accident location. This is especially true in many pin situations. Wading is often combined with swimming and perhaps using your boat to reach the victim. Wading is especially useful in shallow water, water below knee depth. Wading has it's own unique challenges. If you have ever tried walking on wet rocks (especially muddy rocks), you will notice they can be quite slippery. Moving current compounds the challenge in staying upright. Most wading techniques add one or more "legs" to form a more stable posture.
One danger we always need to keep in mind is the possibility of foot entrapment. Take your time when wading. Sometimes it may be difficult to look under the water surface. While placing weight on your brace, feel the surface bottom with your toes for nice stable positions. Once both feet are firmly planted, you can then move the brace. Always be prepared to swim either on purpose or by accident. Swimming is actually faster and safer as the water gets deeper. Avoid standing in fast current where possible, this is known as the "Safe Eddy Rule". A safer approach is to mix short swims in the fast water with rest stops in the slack water of an eddy. Here is a good article on wading technique from a fire & rescue journal: Wading Technique Article