Bass strings down an octave; treble strings up an octave. MXR Bass Octave Deluxe and Electroharmonix POG
Here the Submarine is on the high strings. The effect heard is (in order of the chain) an EHX Pitchfork, a Fulltone ChoralFlange and an EHX Holy Grail.
Here is a bass effect again. The Pitchfork is a digital octave pedal similar to a Digitech whammy. Here it is controlled with a Roland keyboard pedal. The Submarine allows the glissando to be applied to the bottom two strings.
Here is the Submarine being used with a good amount of gain. A small amount of delay and compression is applied using Boss pedals. The overdriven sound is achieved with an Audiokitchen Big Trees into an 8" speaker cab.
Pick out melody lines with the Submarine. Play rhythm at the same time. Here's one way to get two different sounds from your guitar.
So what are you waiting for?