The pipe originates from the small blockhouse immediately to the west of the larger blockhouse just below the rest rooms at the west end of Breakwater. It goes out on a heading of 030. So...if you were out in the water and were directly over the pipe, you could take your compass and sight back to the small blockhouse (which will appear to the right of the larger blockhouse) and you would note a heading of 210 (the reciprocal of 030). This is one way of lining yourself up with the pipe. An even better way is to get out to sea and look for the traffic light on the northeast corner of the intersection of Foam and Drake. That light is very easy to spot when you're out to sea in the right general area. If you line this light up with the right hand edge of the small blockhouse mentioned above, you will be directly above the pipe.
When you go down to find the pipe, it is best to start down where you are on a known side of the pipe. Otherwise, you might land just a few feet away but not see it, and then you don't know what direction to swim. If you use the stoplight to line yourself up, I suggest moving off to the west about 20 feet and then going down. Once you see the bottom, start swimming on a heading of 120 and you will bump right into the pipe. Or, if you go down on the east side of the pipe, swim at 300 and you'll hit it. Either way works, as long as you're not off the end of the pipe.
To know how far out to sea you need to go, you need to remember that the heading from the end of the pipe to the red beacon at the very end of the Coast Guard pier is 135. As long as you see less than 135 degrees when you sight that beacon, you're still along the pipe.
If you don't have a compass, you should! But without one, you can still swim out and line up the stoplight I mentioned with the right edge of the blockhouse. Go out even with the gate on the pier and move off to the west about 20 or 30' from where the stoplight lines up with the right edge of the blockhouse. When you start down, orient yourself so that you're swimming toward the pier and wait until you see the bottom before you start swimming. You should find the pipe after about 20'.