It's 5.30pm in the Panorama Bar on the Viking Surkov and everyone should be relaxing over a drink after a busy few sightseeing days in Moscow. But a conflict is brewing.
Our river cruise boat, Viking Surkov, is about to enter the first of 18 locks that we will be passing through as we sail from Moscow to St Petersburg - dropping 196m on the way - and group A has chosen seats inside the bar to get a good view.
Unfortunately, group B is taking up position on the railings outside, blocking group A's views. "They don't even bother to look," one American moans.
Hands wave, voices are raised, windows are tapped. "Are we going down yet?" a passenger asks as we sail into the lock, revealing his (rather poor) grasp of the principles of lock-keeping.
Locks, I soon discover, are a highlight of a Russian river cruise. Next day, I join group B at the front of the ship to snap the moment we enter Uglich lock, a fabulously over-the-top structure that could only have been designed in Stalin's time.
We can see the mast of a ship in the lock; so we stand, eyes peeled, waiting for it to rise and exit, so we can go in. Ten minutes, 15 minutes, 30 minutes pass. "I think we've hit the lock-keeper's lunchtime," one punter comments.
I suspect he is not far wrong. The Soviet Union might be long gone but as my few days on Viking River Cruises' Viking Surkov have shown, its service standards - or lack of them - have only slightly improved.
Iced water is served with lunch and dinner on the ship, but whereas most cruise-ship waiters would have you drown in the stuff, constantly refilling your glass, on the Surkov you not only have to ask for it, but ask again if you want a refill.
Plates are brought and cleared at random - there's no such thing as "ladies first" here - and coffee cups are filled to overflowing, which makes for a messy first sip.
For the first few days I got the impression that the restaurant staff would have been happier anywhere else but on the Surkov, but gradually they relaxed and even started to smile and venture more words in their good, but whispered, English.
It especially made my day when Anastasia approached one morning in the Panorama Bar - my regular haunt for continental breakfast, as it is more peaceful than the main restaurant - and asked if I would like some hot water, my usual, if unusual, morning tipple.
That was the moment I started to believe the Viking crew are the best trained on any river boats in Russia.
Viking also maintains that the Surkov is the best boat in Russia following an upgrade.
The work included making some cabins bigger, adding en-suite facilities for all and a lift, which is handy for people with mobility problems as the stairs are steep. While it is no doubt much better, the boat is far from perfect.
My cabin is comfortable, if compact, with a reasonable-sized bathroom and shower, and opening windows, which is nice (none of the cabins has balconies) but it's on a corner of the corridor, so the door opens on to a wall butting into the room. I've nearly walked into it several times - and that was before the vodka tasting evening.
Also, the top deck is not big enough for all 210 passengers when the sun comes out, which happily it did on several days, and the Sky Bar was cramped during the Russian history lectures laid on by our resident guides on sea days.
There are six guides on the boat, each assigned with a group of about 30 passengers. The guides hand over to local guides at each stop and hang around to make sure no one is lost.
Nevertheless, we did manage to leave someone in Moscow. Before disembarking, you hand in your room key and get a boarding pass in return, so they must have known he was not on board, but these boats are more punctual than Swiss trains and waiting is not an option. Luckily, they were able to get him to the first lock, where he jumped aboard.
Viking's river cruises from Moscow to St Petersburg, or vice versa, sail along a combination of rivers, lakes and canals. There are three days' sightseeing in each city at the start and end of the cruise and five "sea" days in between, with visits to such fascinating towns and villages along the way that the slightly haphazard service and unexciting food pale into insignificance.
Meals are served in one sitting - but you can sit where you like - and food is what Viking calls European, tailored to US tastes. It does the job but is nothing special.
Daily tours are included in the cost of the cruise - prices start from £2 795 (R44 000) for 12 nights' full board, including flights and transfers on the Viking Surkov this year (including a premium for the newly refurbished vessel) - and there are optional excursions in the big cities, such as Moscow by night for 29 units (R360) and a Cossack folklore show in St Petersburg for 25 units (R310).
The unit is the euro in disguise. Russian regulations forbid boats from advertising foreign currencies. So Viking has created its own.
"The authorities do come on board and check," Viking River Cruises' chairperson Torstein Hagen confided with a sigh.
He is on my cruise to see Surkov in action after its refit. "If they find you breaking the rules, you're closed."
The old Communist Party would have been proud.