New (to me) Submariner woes. Water involved

[river rat1]

So last week I finally took ownership of my grail watch, a no date sub. I bought the watch from Bobs watches and everything went smoothly. A few days after I owned the watch I was swimming all day and later that night as I was admiring my new watch I noticed that the case back was super loose. I emailed Bobs watches asking what I should do and I haven't heard back from them yet. I don't see any moisture in the watch but have yet to remove the back. Anything I should be doing, or just wait to hear back from Bobs? Thanks guys!