Stunned tourists captured the two big cats scampering into the water on their mobile phone in Africa last month.
See also: Crocodile and elephant go into battle
But the fierce crocodile spots the animals and rushes towards them in Wilderness Safari's King's Pool in Botswana.
The shocking footage shows the large reptile attack the smaller cat but his heroic sibling fights back and helps him to safety.
The two lions went for a swim in the river
The younger lion somehow scrambles unharmed to the shore on the far side, according to the safari guide.
The other creature makes it to the side on which he started.
One of the terrified witnesses said: "We found them [the lions] by the Linyanti river between Botswana and Namibia, and watched them drinking water.
"We thought they would come back out of the water but then we saw the younger one going back in."
A hungry crocodile pounced on the smaller lion
Somehow the tourists said both lions scampered away unhurt
"Our guide saw a crocodile on the right and we saw the older one look at the croc.
"Again we thought they would turn back but the younger one kept going in deeper.
"The older one hesitated and then followed him in.
"As they swim across the crocodile speeds up and while we all watched with our hearts in our mouths, the younger lion was attacked by the crocodile."
"The older one then attacks the crocodile and effectively saves his younger brother before going under the water; the younger one started swimming back and we thought the older one was gone, but then we saw him pull himself into the reeds - incredibly they both survived with no injuries!"