Hippo are faster on land than you might think. Should you come between them and their safe haven, they can attack, or simply run over you to get back to the water. The best camps and lodges will provide an escort, often armed, to escort you.
Another way to avoid crowding hippo is to stay in the shallow waters when canoeing or boating, giving hippo the freedom they prefer in deeper waters. This is especially useful on the Zambezi above Victoria Falls, the Rufiji in the Selous, or the tributatires fo the Okavango Delta.
You may still encounter the occasional rogue or Angry Young Male, trying to prove himself, (which also happens with bull elephant) and the injured, ticked off at the world because they’re in pain.
Even experts in animal behavior have close encounters. My friend Joan Root had her face mask ripped off by a hippo when filming underwater at Mzima Springs, the tusks missing her face by millimeters. The water was murky, and the hippo felt cornered. Alan Root didn’t get off so easily; the same hippo bit his leg, which gave fodder to George Plimpton’s New Yorker profile “The Man Who Was Eaten Alive in Africa.”
To photograph hippo, use the concrete bunker at Mzima Springs, a telephoto, or shoot from a vehicle. Shoot from a boat only if you feel secure about your gear not getting drenched, which is to say, in a large, stable vessel. Do not use flash photography with animals; at dusk or night, use very high speed film, or simply watch hippo with night vision binoculars, or do as I did, regard them by the light of the moon.
Those silver bullets dashing toward Lake Naivasha remain one of the more dreamy images I have of Africa. It’s a good idea to pull that camera off the front of your face once in a while anyway; you experience things differently, vivid in the mind’s eye.