To get the diagram above I did the following:
@startuml
skinparam ArrowColor #4173C0
skinparam Swimlane {
TitleFontColor black
TitleBackgroundColor #C2DEF8
BorderColor black
BorderThickness 1
}
skinparam Activity {
BorderColor #A8D0F6
BackgroundColor #C2DEF8
DiamondBackgroundColor #FAE1B8
DiamondFontColor black
DiamondBorderColor #F7D499
}
|swinlane1|
:first;
:second;
|swinlane2|
:third;
if (foo) then
:something;
endif
|swinlane1|
:back to swinline1;
|swinlane2|
:back to swinline2;
@enduml