Shin and Uehara each had three consecutive birdies on the course's second nine in taking a one-stroke lead over a group of six players, including defending tournament champion Momoko Ueda, with 10 more players at 2-under.
Among those tied with Ueda is Choi Na-yeon, who had a bogey at No. 17 that cost her a share of the lead. The large group at 2-under includes Inbee Park, who won the LPGA tournament in Malaysia three weeks ago and was second last week in Taiwan.
Windy conditions hindered play.
Uehara notched birdies at 4 and 8 but had a bogey at the 10th hole. She came back with three straight birdies over Nos. 11-13.
Shin played the second nine first and jumped into the lead with birdies on Nos. 12, 13 and 14. She added birdies at the second and sixth holes but dropped into a tie for first with a bogey at No. 9.
Swim Week Miami Beach 2014 [PHOTOS]