Well I've seen all the legendary fishes in the sea but I've had trouble catching
Fire Dragon &
Mossy Moses. but I was lucky to Catch
Speedy Lou (More that 7 times) and
Glittering Girl (2 times) and I
Just caught
Fogbell .
^I got a screen-shot when
Fire Dragon first appeared ,but I didn't take one with
Mossy 
but if you need my advice you have to be
Patient a little Just throw the lure as far as you can but of course you have to have the
Legendary Lure which means you have to
Master fishing to get it, anyway after you throw the lure you have to get it at the very bottom of the sea and keep it there, and keep scaring away any fishes that can get the lure, maybe you will need 10 minutes until a legendary fish comes but I'm not sure, when a legendary fish get near you will notice that all the fishes on the screen will swim away and the Fish will finally appear on the screen alone in the sea. and then it will tell you to click as fast as you can to keep him from getting away, and then you have to reel it in doing that you have to move the mouse in circles, do it repeatedly until you catch it but sometimes you have to catch the reel when it spins out of control by just clicking on the circle that's spinning . by that you caught a
Legendary Fish !!
BTW: You can Find Legendary Fishes anywhere !