Cardiff swimmer Ieuan Lloyd set a new 100-metre freestyle Welsh record of 49.09 seconds as he finished fourth in his heat at the World Short Course Championships in Istanbul.
The 19-year-old Cardiff swimmer has been in impressive form over the past week, lowering his own 200m freestyle Welsh record three times in two days.
Swansea swimmer Jazz Carlin also set a Welsh record in the 400m freestyle.
Her time of 4.02.45 was only good enough for fifth place in the final.
But Carlin's performance has added to a succession of Welsh best times set at the event.
Georgia Davies set a personal best in the 100m backstroke final and on Wednesday Jemma Lowe won bronze in the 200m butterfly.
Georgia Davies and Lowe were part of the 4 x 100m medley team that finished fourth in the final.
Lloyd has gone from strength to strength over the past month, having originally set Welsh 200m and 400m freestyle records at a short course meet in Japan in November.
David Davies, the 2004 1500m freestyle Olympic bronze medallist, had held both records for three and a half years.