The owners of a Limpopo game farm on Friday said the vet, who was hired to tranquilise a stranded hippo, arrived four hours late.
The one-ton animal died earlier.
Solly had spent four days in a pool at the Monate Game Farm after he was kicked out by his pod earlier this week.
He had been in distress after the swimming pool was drained earlier to prepare for a rescue operation.
Game farm manager Ruby Ferreira said, "They just arrived here 10 minutes ago and he died. We've been waiting since 7am. I'm very upset that he died."
Meanwhile, the vet who was hired to tranquilise the hippo, said the animal's prognosis was never very good.
Vet Alex Lewis said the animal was under immense stress earlier, when the pool was drained, in preparation for the rescue operation.
"I think the whole experience was incredibly stressful for him."
Meanwhile, Cape Town authorities have warned the public to be on the lookout for a two-year-old hippo that is on the loose.