An inquest into the death of a baby boy who suffered brain damage after nearly drowning in a Bumbo seat in the shower will examine safety around water.

The coronial inquest has been told the child, who died aged six months in January 2013, was left in the shower unsupervised for seven minutes.

The baby fell out of the seat, which then blocked the drain, allowing the shower cubicle to fill with water.

He was unresponsive when his mother found him, and she gave him CPR until paramedics arrived.

Paramedics took the boy to Joondalup Health Campus, where his heart was restarted.

But the boy had suffered irreversible brain damage and died with his parents by his side.

A post-mortem examination concluded the cause of death was bronchopneumonia and hypoxic brain injury following immersion, or near-drowning.

Bumbo seats previously recalled after safety concerns

The court heard that leaving a child near water in a Bumbo seat was contrary to the advice of the manufacturer.

The seat did not have restraints or a harness.

Bumbo seats are made of low-density foam and are ideally used on flat surfaces to help babies sit up.

Over the past nine years, the US Consumer Product Safety Commission and Bumbo International in South Africa became aware of at least 50 incidents around the world where babies fell while seated on raised surfaces like tables and counters.

There were 21 reports of skull fractures.

In 2007, one million Bumbo seats were recalled to attach additional warning labels, cautioning against putting the seats on raised surfaces.

In August 2012, the US Consumer Product Safety Commission, with the cooperation of the South African manufacturer, announced a further voluntary recall of Bumbo seats worldwide.

Manufacturer offers free restraint belt

The commission said parents should stop using the seat until a free restraint belt had been installed.

The Consumer Product Safety Commission of Australia duplicated the message, and a recall was issued, but it is not known how many were retrofitted.

Counsel assisting the coroner Sergeant Lyle Housiaux told the court he had recently searched for second-hand Bumbo seats and found 950, used and new, available on online sales site Gumtree alone.

He said about half did not have a safety harness.

Sergeant Housiaux told the court the manufacturer still provides a free harness system via internet orders.

The consumer can attach the harness using simple instructions.

Inquest to examine child safety around water

The inquest will focus on the issue of child safety, particularly around water.

The court heard the Bumbo seat was not recommended for use as a bath seat, and there was a further warning that a baby should not be left unattended.

Counsel assisting told the court Kidsafe WA advised all children should be closely supervised, within arm's length, when in any water, including in bathrooms.

Kidsafe WA said it only took a few seconds in five centimetres of water for a child to drown.

Drowning is the fourth leading cause of death of Australian children.