PRW - the only ones I could keep in were the older Speedo honey stirrer type - everything else just floated off. they were similar to the Speedo Biofuse ones but with a straight peg, but they stopped making them some time ago and nobody else does anything similar now.
EDIT: just found these - http://www.comfyearplugs.com/macks-aquablock-ear-plugs.html
then I tried mouldable ones and they work fine as well so perhaps try them??
Edited: 10/01/2012 at 12:24