Posted March 12th, 2018, 06:40 PM
Did a Carnival Baltic cruise in 2013 from Dover and quite a few UK and US passengers were told they had to stay on the ship in the St Pete's port as they had no tours and visas.
One could take from that they were definitely allowed to board without Russian visas.
For those of you on private tours and ship ones the reason you didn't need a Visa is because it was included in your tour. Most nations need a visa in Russia- I can't remember which countries are exempt.