You don't mention whether your in the Hero or Villain version of those islands, so my suggestion would be to make sure you're looking at the right info for the zone. (Remember, Hero badges are actually part of Peregrine Island's map.)
Blondeshell (1381 badges) - My other badge hunters
VidiotMaps Master Cartographer
MArc #87989 - Enter, The Conglomerate
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Basically, what Blondeshell said. Those exact islands are in 2 places in the game. Their badge locations are not interchangeable. If you are actually in the Monster Island Zone (took a submarine from north of Grandville), then use Monster Island's badge maps.
The areas north of PI are officially named Tempest Quay and Cutlass Isles. In fact, the "neighborhoods" inside the Monster Island Zone are even called the same thing, but if you are just in PI, then make sure you look at PI's badge map instead.
On a side note, if you want to really explore (and not just get the badges), be sure to visit the NW corner of the Monster Island Zone. 
(Spoiler: click here)
So...I'm out picking up new exploration badges and nothing on Monster Isle or Monkey Island seems to be there. I don't have them, there is no badge marker, Vidiot and Titan agree on the coordinates, but......no badge.
Anyone else run into this?