cool looking dude! my first thought was the Colomesus asellus if its from south america BEFORE I SAW THE PICTURES but they do not have any dots like this one or has the similiar design
for your guess of a figure 8 puffer...its very possible its a Tetraodon biocellatus however I'm not that well versed in puffers
similiar figure 8 like yours...http://www.**************.com/forum/ug.php/v/PufferPedia/Brackish/T_Biocellatus/PB2305201_1_.jpg.html