Standard Diplomacy Rules Apply

The Dneiper River runs from Kief to the Black Sea. All territories bordering this river act as coastal territories. For example, a fleet can be built in Kief and can move to either Cumeria or Patzinakia, fleets and armies can cross the river (eg. an army can move from Patzinakia to Cumeria)

Croatia is a landlocked territory despite appearing to have a coast. It is blocked from open waters by Venice.