A mysterious red dot in Salt Lagoon?

[MH DOOM]

Chasing a treasure map's loot, I found my way halfway across the Caribbean to this remote spot called Salt Lagoon. After getting everything, including the secret, it shows me the completed list (all chests, sync'd, etc), but there's this red dot on the minimap and the map menu that has no explanation.

Here's a couple of screenshots I took.

In-game Minimap[i.imgur.com]
Map menu[i.imgur.com]

I just wanted to know if anyone knew what this was about? Thanks.

[ClonE]

It's the restriced zone an assassin contract spawns in

[MH DOOM]

Wow, really? Well it'll be easy to keep out of that spot.