Boyle, who won gold in both the 800m and 400m freestyle, recovered from a conservative start to hit the lead at 100m. She had slipped back to third at the 150m mark in a tightly fought battle as teammate Hind, out of sight and out of mind in lane eight, challenged for the lead.
Spaniard Melania Costa Schmid, who just missed a spot in the finals at the recent world championships, pushed clear to win in 1min 57.98sec. Boyle showed her fighting qualities to get up for second in 1min 59.19sec, just ahead of American Karlee Bispo with Hind only .25 away from the podium in 1min 59.56sec.
Snyders collected silver in the 100m breaststroke to go with the gold he won in the 200m breaststroke, and has a chance for further success in the 50m on Friday.
The 24-year-old again went into battle with Lithuania's Giedrius Titenis after the pair dead-heated for the gold medal in the 200m final. Snyders was on schedule for a potential sub-60 seconds effort, as he went through the 50m mark faster than his national record effort in Shanghai. He lost some fluency in his stroke over the final 15m as Titenis edged past to win in 1min 00.39sec with the Snyders .3sec behind.
Earlier both Gareth Kean and Kurt Bassett recorded personal bests but finished just out of the medals in the 50m backstroke.
Kean, 19, took .35sec off his season best from the heats to clock 25.49sec for fourth. He was less than .3sec off Daniel Bell's national record.
Bassett, a 200m specialist, was fifth in 25.52sec with both swimmers enjoying a strong meet. Kean won a gold and bronze while Bassett picked up a bronze in the 100m.
- NZPA