Pretty much all safari destinations and lodges offer bush walks as complimentary activities and there are also several walking trails available where you explore the bush on foot.
This is a very different experience and demands a lot from wildlife photographers. The moment you leave the safari vehicle and set foot on the ground, you are entering the animals’ world and you will find yourself within their hierarchy. The plains game will run away from you and when you walk into elephants or lion they might charge you.
Do bush walks only with a professional guide. Be careful with the choice of the equipment you take with you. Everything becomes very heavy quickly and you should be light footed when walking in the bush. Don’t think you need to bring your entire photo backpack in case you would need a special lens. Take one camera with a zoom lens and rather put some water and food in the backpack to stay fit.
Watch your steps and dress according to the environment. You will feel very different from being on a vehicle and that will reflect in the images. Rather do a few bush walks to get used to it. When you start feeling comfortable on foot, your focus will be again on photography, allowing great images.
Try it and you will feel the difference. Seeing a leopard on foot is a completely different experience.