What should I do with my crank/bottom bracket? I just got this mountain bike almost 3 weeks ago. I took it for a long ride(120km back and forth). We encountered heavy rain during our ride, we were riding on a highway back then, there's flood water flowing everywhere as you would imagine but not enough to submerge the bottom bracket. 

Everything is perfect until the next day. I took the bike for a spin, I felt something inside bottom bracket snapping. I immediately inspected the crank to see if its loose but its not. I then moved on investigating on the pedal, as it may give this feel as well but its not. 

I really think this has something to do with the bottom bracket. I then took it back to the bike shop I purchased is from to be checked. What I was thinking is flood water went in and affected the performance of the bottom bracket, I'm thinking of asking them to repack my bottom bracket however. The shop mechanic won't do it, he told me that its too soon for a bottom bracket repack. The snap that I feel inside the bottom bracket is not extreme, as a matter of fact you wont feel it if you don't pay attention to it. 

Its just irritating for me specially if I'm not experiencing anything like that before the long ride. If you shake the crank its rock solid. What should I do? I'm using Trinx XC3 treker, not top of the line but high quality.
If you just bought it, the shop mechanic should remedy the problem no matter what specific part is to blame. If not, threaten to return the entire bike and take your business elsewhere. It should be as simple as that.