Frank Velasquez scored twice for a team-leading eight goals and Agustin Ruiz added his fifth for El Salvador, which by reaching the semifinals achieved the best finish for a CONCACAF team at the Beach Soccer World Cup since Mexico was runner-up in 2007.
It will face Portugal, which defeated Los Cuscatlecos 11-2 in the opening game for both, on Sunday for third place. The match will proceed the final between Brazil and Russia.
Dimitry Shishin and Ilya Leonov both scored in the first five minutes to put Russia ahead. Ruiz pulled El Salvador within one 1½ minutes later, but Egor Shaykov and Alexey Makarov replied before the end of the period to extend Russia's lead.
Velasquez tallied twice in the second period, but each time was matched, first by Shaykov's second goal and then by Egor Eremeev to leave Russia with a three-goal lead entering the final period.
Yury Gorchinskiy ended any hopes of a comeback with a goal with a minute and a half remaining.
El Salvador's three victories to reach the semifinals came after it had lost seven straight at the Beach Soccer World Cup, including all six matches in two previous appearances.