Here is the full list of all 10 Mysteries Under Lake Ophelia achievements.
Buy out the whole shop.
Encounter the Mysteries Under Lake Ophelia.
Empty out the entire lake (and ponds).
Catch the Prototype Fish.
Catch them all.
Cook a Dubious Dish.
Cook an Average Dish.
Cook a Glorious DIsh!
Obtain every Lure.
Obtain every Fishing Rod.