You might have seen this, but this is a satellite map for AC. if you follow AC to the very far north (past the area that is missing or in low resolution, the location of Tranquility Bay is not marked, but it is located near Sueno del Mar and what is marked as "Nova Shrimp Farm".

http://www.wikimapia.org/#y=17923454&x=-87961049&z=15&l=0&m=a&v=2

Feel free to send me an email after we return Nov 20 and I'll fill you in on more info - austin at austincrossley dot com.