First level: Secrets: Blow up the crack in the wall and climb over and dive into water to get RPG,After power is on slide down ladder and blow up item to get quest item,in power core blow up air vent shield and get biography.
Second level:Secrets:Behind the large fan and when activated jump over the water to open the dive tank (When you come out of water kill Pig cop),all other secrets are behind differtent doors.
Third level:Secrets:Go to the right of the wall and blow up the large rock (keep going through to find more secrets),When at tower blow up four squares to enter when detenator is input. Funny: When duke is climbing the ladder near Jane he will say-and I'm climbing a ladder........to heaven.
Fourth level: Hints:when you enter water blow up crate for torpedeo launcher (under water RPG) and before moving kill shark above you (sharks are very common) and sometimes you will in counter a phsicic Necro brain.