The West Indies' cricket tour of South Africa hit a new low when they were bundled out for 122 in under 34 overs to lose the third one-day international by nine wickets at Buffalo Park in East London.
The Proteas chased down their modest target with 25.2 overs to spare for the loss of only left-handed opener Rilee Rossouw as Hashim Amla finished unbeaten with 61 and Faf du Plessis not out 51.
South Africa hold an unassailable 3-nil lead ahead of matches in Port Elizabeth and Pretoria next week.
Imran Tahir had the best bowling figures for the home side of four for 28, but the pick of their attack was seamer Vernon Philander, who removed the dangerous Chris Gayle for one run on his way to three for 27 in eight overs.
After 730 runs were scored in the second ODI in Johannesburg, only 245 were needed in East London as West Indies capitulated on a wicket that was more of an even challenge between bat and ball, but nowhere near as hazardous as the tourists' low total suggests.
Marlon Samuels top-scored for the tourists with 26.