Serving as the U.S. team Co-Captain, she swam in the preliminary heats of the gold medal-winning women's 4×100-meter freestyle relay in the 1964 Tokyo Olympics, though she did receive a medal as she did not swim in the finals.

[3] Diverse in her mastery of strokes, by her Junior year, her swim specialties included freestyle, backstroke and individual medley.

She placed a very close second in the National 3-Mile swim in Huntingdon, Indiana in 1961 and trained for the Pan America games in her Junior year.

Her Olympic swim in 1964 would utilize her sprint skills and demonstrate that her demanding daily workouts under Don Gambril had improved her times.

[9] Swimming for Rosemead and Gambril in May 1962, Jeanne demonstrated her versatility at the AAU age group meet in the 15-16 year old category, by breaking records in the 100 and 200-meter freestyle, and as well as the 200-meter medley.

[2][11] In finals competition, Hallock represented the United States as a 17-year-old at the mid-October 1964 Summer Olympics in Tokyo, Japan and was a team Co-captain.

[15] When Jeanne won the 100-yard freestyle as an 18-year old at the April 1965 AAU Indoor championships, she was a Physical Education student attending Cal Poly in Pomona before she transferred to USC.

[18] As mentioned earlier, as a post-Olympic swimmer, Hallock swam as part of a City of Commerce 400-yard Medley Relay that included teammates Mary Campbell, Sandy Nitta, and Sharon Stowder, and smashed the American record with a time of 4:06.8 at the 1965 AAU Indoor Championship.

In 1965, Jeanne was a member of the United States Swim Team that toured Wales, England, France, Monaco, Portugal, and Italy and Spain.