WATER scientists say fish and other ocean life may face risks associated with coal seam gas mining.
Professor Craig Simmons, from the National Centre for Groundwater Research and Training, says it's possible contaminated groundwater could get into oceans.
The water flows into the ocean underground through old river channels that have since been buried, known as "wonky holes".
"If there's any contamination in the groundwater on the mainland and they intersect with one of these wonky holes, they're definitely going to take out the chemistry as well as the water," Prof Simmons said.
"It's certainly not impossible that something like that could happen. I've not heard of it yet but there's certainly nutrients that are taken into the ocean so there is that possibility."
The CSIRO has previously said that fracking - the process used in CSG extraction - posed a low risk to groundwater quality through contamination, and predicted groundwater levels would fall in some places.
Prof Simmons said a research colleague was convinced coastal ecosystems in some areas were strongly dependent on freshwater seepage, but more work needed to be done on the precise nature of the relationship.