A second man charged over the cruise ship death of Dianne Brimble has pleaded guilty in a Sydney court to involvement in the incident.

Letterio "Leo" Silvestri, from South Australia, pleaded guilty in the Downing Centre District Court on Monday to concealing a serious indictable offence.

Ms Brimble, a 42-year-old Brisbane mother of three, died 100 nautical miles out to sea on board the P&O liner Pacific Sky in September 2002.

She had ingested a toxic mix of alcohol and the date rape drug known as fantasy.

Her body was found in a cabin belonging to Silvestri, Ryan Kuchel and one other man, who were also charged after a 16-month inquest into Ms Brimble's death.

Last week, Kuchel also pleaded guilty to hindering a police investigation.

Kuchel was sentenced to an 18-month good behaviour bond.

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