Well, so far I've only been able to do it on the full Windows 8.1 app.
I already had Megalodon at the time I got the last update. I just needed 250,000 to purchase it. Just like swiping between sharks to get to it, except it doesn't picture it.
I've really been enjoying playing with Big Daddy, but it takes a really long time to grow it. Growing each level 1 to 10 takes as long as all levels on the Great White. For example, going from level 1 to 2 seemed to take as long as it took me to grow the Great White all the way to level 10. Perhaps it's not quite that way, but it is WAY longer than other sharks to level up. Since it's the last one I have to get, it's worth the wait, I suppose.
Next up, I'll be wanting a bigger world to play in. I regularly get over 25 million points per play now, without ever paying gems to continue. When the shark dies, I just let it die. Pretty easy once you have the right shark and equipment and strategy.