Riverine
get near the river.Take out secondary weapon. lie down on the floor. hold triangle /_ and move into the water. keep holding triangle dont let go and go as deep as u can. Good for hiding and surprising an enemy

Thin Ice
Where seals spawn go right and walk toward the house. on the back of the house(opposite side of where the 2 windows and the front door is) take out ur secondary weapon. there should be a climb side wif the square button showing. lie down and move backwards. when the climb is gone move forward. when it reappears, quickly press triangle then square. you should be in a weird position against the wall. Hold triangle then hold L. then move left until u c a tree. let go off L and move back. then once ur on the mountain let go of triangle. then move toward the tree on the mountain. move left of the tree u c. then walk into it slowly. screen should become blue. move left and right for a while. u should teleport underneath the map. if u dont ur pernamently stuck. screen shots coming soon.