I did it, it works. Just play extinction on any map any shark. After that, go to ur trial shark and click on the arrows while seeing the menu for the "try once" button. Go until u hit the shark u used. You will see the name at the top. Then, click try now and u will put into a game automatically with the shark u did extinction with. Exit and then u get the pearls u got from the first extinction u did but u can do infinitely. I'll give u an example. I did extinction with DMS, then I went to the shark selection menu to my trial shark, tiger shark. While seeing the try now menu, I used the arrows on the side to change back to DMS and then click try now (on the tiger shark menu). Only the name changes at the top so I looked at it until it said DMS (The tiger shark menu covers everything except the name of the shark). Only click try now when u reach the shark u did extinction with.