World short course champion Boyle finished second in the 800m freestyle, Gareth Kean was second in the 200m backstroke and Glenn Snyders placed third in the 100m breaststroke.
Boyle was run down in the final 200m by double London Olympic medallist Garcia Belmonte of Spain in the final of the 800m freestyle.
The New Zealander made a fast start in her first competitive swim since mArch's national championships before Belmonte hit the front at the 600m mark, going on to win in 8:26.00 with Boyle two seconds behind. Wellington open water swimmer Emma Robinson finished eighth in the final.
Boyle returned to the pool to finish fourth in the final of the 200m freestyle in 2:00.47.
Kean showed plenty of pace in the 200m backstroke final, going through the halfway point in a slick 57.07 but was eventually nabbed in the final 50m by European champion Yanick Lebherz of Germany, who won in 1:59.02. The Wellington swimmer was half a second behind in second.
Snyders qualified second fastest in the heats of the 100m breaststroke but had to settle for third in the final. London Olympic gold medallist Cameron van der Burgh (RSA) took out the final in 1:00.38 ahead of Pan American Games medallist Felipe Lima (BRA) and Snyders, who clocked 1:01.12, which was faster than his morning effort.
The New Zealand swimming team are competing in two of the three meets that make up the annual Mare Nostrum series in Barcelona today and tomorrow and Canet en Roussillon on 15 and 16 June.
