Apologies from a newbie if this has already been covered but I thought that this information from Jane's Fighting Ships of World War I might be of interest to those intending to include ships of various sorts in their campaigns. The details seem to date from late 1919. Most of the big stuff had been either scuttled, disarmed, or otherwise rendered useless[including the 'Pantelimon' aka 'Potemkin' of Eisenstein fame], or taken over by the interventionist/allied powers, Britain, France, Italy and Greece. Denikin had a fair number of destroyers and gunboats attached to his forces, the three gunboats carrying two 6 in guns apiece. There's a note on the 'Bolshevist Volga Flotilla', 12 destroyers including the 'Karl Liebknecht' and four submarines: 'These ships have access to the Caspian Sea, provided there is free passage to the delta of the Volga.' There were 18 armed barges in the Sea of Azov and on the Don, armed with single 6 in or 3 in guns, all in the service of Denikin. The only reference to river patrol boats mentions four 'Danube Motor Patrol Boats' of 24 tons, carrying one 3 in mountain gun and one machine gun, 'transported from the Amur River during the war.' It doesn't state which group had control of these.
Sorry if this is all old hat to regular and veteran readers but I thought it might be useful.