Getting better at Crysis Warhead

I'm playing and replaying the game from the beginning, trying new methods to attack. I'm starting to use the suit features (strength, shield, etc) more efficiently, and I'm using the terrain to my advantage. I kind of prefer the first chapters, and not the alien ones, but I'll get to these later on. I'm playing more with the environment, blowing up buildings with grenades (it's fun). It appears you can also swim to the submarine base, but you still have to open the submarine.