The family of Fistulariidae (Flutemouths) are a small family of fish (with just 4 species) that we regularly see in Sydney harbour. Much like the seahorses and pipefish they have a long snout and tubular body. But these fish are much larger and can grow 2 metres in length.
When they are calm they have no real colour and as soon as they feel threatened or surprised they change their colours and display a distinct banding. It is quite impressive and can happen very quickly.
In Sydney we often see the species called the Rough Flutemouth (Fistularia Petimba) in Sydney harbour.