Rob and Lorelei enter boat kitchen to inspect it. You can see through the door there is a flattering American flag on the boat. However, there is no flag on the boat in any other scene in the whole movie.
Both on boat go for swim when he turns on his back is a black tattoo and around tattoo on arm but on beach no tattoo (covered with makeup?)
Lorelei left her iPhone SE on the boat surface before evening party. On the same party, there was heavy rain on the island. In the morning her phone was fully functional.
There are several stock footage from the air which supposedly show marina in the fictional Saint Aquilla island in Caribbean as the vast majority of movie takes the place there. However, you can clearly see City of Miami in the background.
In the Act III, Lorelei and Rob are going to Miami, and Lorelei said that they are on the open sea. However, camera shot shows they are close to the coast.