Jack moves back a bit and pulls his arms in close as the mermaid climbs into the boat with him. He doesn't want to be perceived as attacking...or to be bitten. His breath catches in his throat when she examines the map and he moves hesitantly, making ready to snatch the thing from her grasp, but she thankfully loses interest. The pirate heaves a sigh of relief and waits to see what thing will next catch her fancy.
The sack is a perfect selection, in Jack's opinion. He grins when she 'tries it on' and smiles to the others, hoping they'll support her choice. "Looks darling, does she not? Truly stunning. ... S'a fine choice, love."
He smiles to her and nods, applauding. For his reaction, you would think it was the most luxurious finery and not faded, dyed burlap.