I'm starting to poke around the sunken city of Collossium. I only have the one mask I bought at the last port.?Does anyone know another source for the masks??

Also, I drug the two chest up and to the shore to try to open them. I don't have a lock picker in my party and Disarn Trap and Pry and starting to be ineffective.?
Are the contents in these two chest important?
I didn't immediately see the entrance to the city and I figure I need to open the chests.

Thanks.