All the DIs will tear you up for the first few weeks. That is how they break everyone down. In fact, they *love* tearing into other classes. That is where you will see people getting class Delta and Charlie chits. In these cases, you actually want your own DI around to protect you from the other DIs.
Imagine boot camp in the movie Full Metal Jacket. The way the DIs yell is kinda like that, but more PC. They aren't supposed to swear, but they can still be ruthless. The first day we met my DI, he came flying into the compartment space and slammed a kid up against a locker because he was moving around when everyone else was at attention. A day later he was demonstrating how to properly cut the tags off of our clothing. One kid put his hand on his face, the DI literally jumped over me, pinned the kid to the ground, and gritted his teeth saying, "How many times have I told you all not to put your hands near your face?" We were exposed to our DI for only 2 days at that point in time, but he definitely made it clear the very first minute he walked in that we are not to touch our faces.
It sounds worse than it is. These are not everyday occurances. Your experiences may differ. But, I promise you, your DI will *not* be your buddy in the first few weeks. You will more than likely dread seeing him (or her). They are supposed to be mean. You are there to learn respect, discipline, and teamwork. If one person fails, you all fail. If one guy wants to be an individual and wear boxers to PT instead of the issued jockstrap, and the DI finds out, you will all be playing in the cold wet sand that is infested with fire ants that *LOVE* to bite. Either that or the grass, which has just as many fire ants.
Just focus on what you are doing, focus on doing things correctly, focus on teamwork, focus on doing *exactly* what your superiors instruct you to do, and you will be OK. If it was *truly* a brutal training program, there would be very few Naval Officers, right? Rarely does anyone fail out of OCS, so it is doable...you just have to give 100% a 100% of the time.
"The object of war is not to die for your country but to make the other bastard die for his." - General George Patton (1885-1945)