particular location in world lags badly

On a fairly new world, I have been playing for a few months, a particular location lags to the point I can play this world anymore. I moved out of the area, and the lag reduced steadily the further I moved. The location is under water in a river with glass blocks, dirt blocks & ladders forming walls, roof and doorways to keep the water out. I have created this construct all though the rivers near my spawn point with no issues up to now. Reducing the number of ladders deployed did reduce lag slightly. After moving away from the lag location, and approaching from the surface with usable lag until I dived in to the water, then the lag resumed. I blindly returned to the surface & logged out. I tried to login and the world would not draw at all. A different world is working fine. Its a bit hard to do a picture since I can't get to the lag location anymore.