I am currently trying to complete the quest "The Nuclear Option" and I cannot find the "old tunnel" to save the life of me. I have been searching for hours and the only thing I have found online says to "Travel to the river in Cambridge, west of Greentech Genetics. Dive into the water and swim to the Public Works Maintenance area. Once there activate the keypad."

Even with this very vague information I am lost and hoping someone on here sees this and can shed some light as to where this tunnel is located. Any pictures/videos would be much appreciated.

Thanks.

Follow the quest marker. It's IN the water. Giant pipe. And you'll be in the water for a fair bit so take some anti rads.