Actually it is not brackish but is simply the white sand or vegetation. Brackish is found in the 'watershed' areas where organic processes, which are essential to the health of the ecosystem, is occurring. This if found usually in mangroves or other wet area influenced by the tide but not in the tidal zone. Also, brackish is used to describe fresh water environments most notably...swamps!
You would need to get a mile off shore to engage the Clear Blue that you see in the Caribbean. In essence, into water sufficiently deep that the reflection of the sky is stronger than the content of the water or floor.
Caribbean Blue would not be what you should expect in the Dunedin waterways.
Best of success,
Annette Lawrence, Broker/Associate
Remax Realtec Group