If you enter the cheats SVWG and HUTR it maxes out your piranhas. Then if you go back to the shop, click SEEDS, buy one more, and click SEEDS again you can keep clicking more and more piranhas infinitely. Sucks that after you do a mission it goes back to 10 and don't appear while you're doing the mission.
 "Deep Sleep"){kind=icon}
 "Feed Us 2"){kind=icon}
 "Run 3"){kind=icon}