Cross-contamination occurs when gluten-free foods come into contact with foods that contain gluten. It can happen during the manufacturing process, for example, if the same equipment is used to make a variety of products. Some food labels include a may contain statement if cross-contamination is likely.
After getting a tattoo, swimming must be avoided until the skin has stopped peeling and all scabs have fallen off. For most people, this means waiting a minimum of two weeks.
As a tattooer, that sucks. You should wait at least 2 WEEKS before being in the ocean or a pool. Not just for the potential bacteria, salt or cholrine, but you want to keep the tattoo as dry as possible. Unless kept dry, it will heal poorly.