This can only be completed on NG+
This is unlocked by not raining at all on the Beach level in NG+
After completing the game go all the way back down the map to the beach level and use only the tornado to throw all of the humans into the ocean.
*I got it after getting hit but some users are reporting that it didn't unlock until they did it without taking damage so if it's not unlocking just avoid the sun. No timer so just be careful
Below is a clip I made showing this achievement's requirements and all tasks to unlock sunglasses for the other achievement