Posted April 16th, 2018, 01:11 PM
Things may have changed since we visited St. Petersburg in 2012 (on a Silversea cruise), but at that time individual visas were not (repeat, not) a requirement for touring the city and environs with a properly licensed tour operator such as Alla. (We also used a guide from Alla, and also were very pleased.)
There has been much discussion of the visa issue on CC and on Trip Advisor over the years, and much misinformation. There is (or was) a widespread false impression that the cruise ship had a "ship's visa" that substituted for individual visas that would otherwise be needed. The fact is (or was) that there has never been such a thing as a "ship's visa," and the "ship's tours" that took people around without individual visas were operated by the same type of tour operators, under the same legal authority to escort visa-less foreigners, that you could book on your own at much less expense and with much greater choice and flexibility of touring programs. It's those contract operators who convinced the cruise lines (or convinced them to tell their passengers) that theirs is (or was) the only legal way for passengers to see the sights without an individual visa.
I can say this with confidence because I have personally seen and read the controlling official Russian governmental regulation. It's worth noting that if you carefully read your cruise line's notices and informational material on this issue, you may find that the pre-cruise material is enough to scare you away from making independent plans, but the on-board notices once the ship approaches St. Petersburg are much more cagily worded. Caveat lector.
A related point to bear in mind was told to me by an acquaintance who'd visited Russia on business numerous times and was in a position to know (if you get my drift): Those friendly tour guides who speak impeccable English almost certainly are active or supposedly former FSB intelligence agency employees. So watch your words carefully. As my acquaintance puts it, there's only one foreign language school in Russia where you learn to speak perfect, unaccented English, and it ain't Berlitz.
To repeat, though: Things may have changed since 2012. You might check the St. Petersburg board in the "Ports" section of this forum to see what's currently being said (by reliable sources, of course).