After getting Dive

[John Tsoukalos]

For most of the game, i haven't had too much difficulty.   There may have been a few times that I felt under leveled and grinded to make up for it, but I feel like I am far behind now.  I went to the area where you use dive for the first time outside of Venesi City.  The trainers underwater have pokemon 6 levels higher than me.  My Pokemon are around level 48.  Am I the apporopriate level or do I need to grind somewhere to catch up?  Any good grinding spots if so.  

Thanks!