User blog comment:Kaido King of the Beasts/Chapter 823: Bibi Heads to Revelly/@comment-24850639-20160414140555/@comment-7606564-20160414154718

In regards to fishman island, everytime I hear about it I'm more convinced that it's going to go like this:

Fishmen protest to move to the surface so the WG with the donations of a mysterious someone (Big Mom), build them a floating island on the surface. The reason I couple WG and Big Mom is that both of them want the fishmen gone. The world government obviously doesn't view them as people. Big Mom needs to exact revenge for the bomb and for them skipping out on candy.

So what do they do? They build the fishmen this nice beautiful island with tons of explosives in the ground just to kill all the fishmen once they arrive.

Luffy discovers this plot by the WG and destroys the new island since it was essentially a trap. So there, he destroyed fishmen island, remains a good guy, and furthers the whole "Luffy vs WG" thing that's eventually coming.