Possible Clues:

• Specialised vocabulary
• The vessel has disappeared, by the sound of it, in a manner of speaking
• Gibberish
• Patois, vernacular
• Lingo of a particular group
• Language specific to an activity
• Inside-baseball vocabulary
• Clash finished? Not quite and few may understand it
• It's hard for a layman to understand Jack can be gas
• Tech specs, e.g