I can hardly believe that I finished this first part of the Mermaid quest yesterday and have moved onto Of Land and Sea.
I've been on this goal since it started back in June of last year, and tried pretty hard with it at first but have been on stop-start for a long time due to non-stop events taking up so much energy. I think it took me longer than sister sister, but was less tedious. I'm super-happy with the look of the Coral castle at level 10, so will take it easy through the next steps. In the end it wasn't the eels that held me up but shells and coral. I don't think my coin collection will ever recover from being hammered so hard in the early stages. I lost count of the millions I've spent. I'm certain it would have taken at least twice as long it I hadn't committed my coin collection to it!