Splasher

For this achievement you need, as explained in the description, to put two splashers in the same place, the first time I believe you can do this is in the level 14 called "Inkorp Express", near the end, you will end up in a room full of splashers where you will pick up the Bouncink, which will unlock the following achievement :


Once you have the Bouncink, go right above you, slightly on the right, you will notice a splasher trapped with a H sign, to get him out of here, shoot yellow paint under his feets and try to get out of the way so you don't collect the splasher, as soon as he is out, shoot directly at him with the yellow paint to the right, if everything went as planned, he should fall right next to the splasher with the P sign, the achievement should unlock here.

If your splasher is stuck on the right wall, simply shoot water at it, he will fall next to the other guy, if he somehow land somewhere else by bouncing on a wall or something else, you can retry by killing yourself with the door, just open it and let it crush you.

If you're confused I included screenshots below, including both splashers locations and the door to kill yourself.



In case the screenshots are not working for some reasons, here is a imgur link : https://imgur.com/a/e5SPR