Whaletails are created typically when a woman crouches, bends or sits. Rarely are they just on display althought it's possible. These situations typically occur in public areas with lots of people such as shopping malls and public gathering locations/events where this will occur. Capturing with a phone is usually pretty inconspicuous although you will need to take caution to not linger too long. Most situations happen very fast so always be in ready mode when searching. Good luck and post any you find here!
U may see a whaletail when a woman squats down to get something from the bottom self at the supermarket , but be warned … a guy was caught on camera doing this and the woman took offence and had him charged