Placid Plastic Duck Simulator

The first collection refers to the "Placid Plastic Ducks" option you can select when choosing a game. To make this faster, don't select the other two duck packs as those don't count towards the three.

Start a game here, pick your preferred map, and let the game run. Your first duck will drop into the pool and approximately every three minutes a new one will spawn. Achievement pops after the third one drops.