Senka met Limpid on his first day in the Zone. They became good friends at the very start, and eventually became members of the Bandit faction. They drank extreme amounts of Vodka together (in Limpid's words: "You'd drown in the amount of vodka we've drunk together!"). Due to this, he always sitting in the base drunk. The player cannot engage in any conversation with him.
Call of Pripyat
Well... uhh uh... you know... - Senka's drunken rambling
He returns in Call of Pripyat, where he is drinking with the mechanic in Yanov. He still doesn't speak, but if the player tries to talk to him he begins to groan as he probably has a hangover. If you choose to have the mechanic unlock the UAV module, you will find his corpse at one of Strelok's group caches, after trying to steal the contents for himself. He apparently died from chemical anomalies.
Senka and Nitro both met each other at Zaton and the two have been travelling ever since, until Nitro settled in at Yanov. Senka now runs errands.