The European Swimming Masters Championships (or "LEN Swimming Masters Championships") is an international Aquatics championships for adults (per FINA rules, Masters are 25 years old and older). The championships are held biennially (in odd years until 2013, then even years from 2016), with competition in all five of FINA's disciplines: Swimming, Diving, Water Polo, Open Water Swimming, and Synchronized Swimming.
Starting in 2016, the competition will be held jointly with the European Aquatics Championships.
References
European Masters Swimming Championships Wikipedia(Text) CC BY-SA