Having experience with drowning countries myself (I'm Dutch), I compiled a list of all countries that could possibly drown their neighbours. In other words: Countries that posses (parts of) lakes of sufficient surface area as to outnumber the surface area of a neighbouring country. How many of those can you name?
It does over the Caspian sea itself (https://share.google/1CxasyFS0ZfdgT59K) and as this is considered a lake, it consequently also counts as a country border