During gameplay press F9 to bring up the console then enter a code below and press ENTER to activate:

next level - Skip level
god - Invincibility toggle
set damage 0 - No damage
destroy all - All opponents dead
load level # - Load level put in 1-99 for #
set bullet # - Get # amount of bullets (Put in a number for #)
set missile # - Get # amount of missiles (Put in a number for #)
reload level - Restart level
set dc # - Get # of Depth charges (Put in a number for #)