Tanner beat US and Olympic champion Cathy Ferguson, who swam aganst Karen Muir and Ann Fairlie in South Africa in 1966, in the 100m backstroke at the US nationals in 1966 She also won seven medals at the 1966 Commonwealth Games. With Hughes, Lay and Kennedy, they won the 4x110 yards freestyle relay at the Games in Kingston, Jamaica.

Ann Fairlie, Elaine Tanner and Karen Muir in 1966.
She met Karen Muir in August 1966 when the Springboks swam in her hometown of Vancouver. Tanner and Muir ended in a dead heat for the 220 yards IM - setting a joint new World record. The race featured the oddity of (Canadian) judges determining Ms. Tanner had finished first, while timers recorded Ms. Muir touching the wall one-10th of a second faster. Under international rules, the record was shared, based on average times.

Tanner was there In Blackpool when Karen Muir broke her first world record in 1965:
Beneath the stands, a young Elaine Tanner was surprised by the tumult. “It sounded like a stampede up there,” she recalled. “I thought, ‘Who would break a world record in an age-group event? Oh my god, who is this girl?’ ”
By the time she was 15, the Karen Muir stood 5 foot 7 with a physique so lean she was called Bamboo. Her Canadian rival, nicknamed Mighty Mouse, stood at five feet 3 inches.
“We looked like Mutt and Jeff together,” Tanner said.