my minecraft lagging

so i keep lagging on minecraft and my specs are hi. i have a core i5 and my graphics card is a gtx 980. i have 128 gigs of ram. so i launched the game on a normal world and its still lagging i even turned off all my background processes and boosted my pc and i'm still lagging especially in the water. please fix this problem. i cant have the screen shot to do this so i don't know about that.