Police have charged a 19-year-old man after he was allegedly found in possession of 55 ecstasy pills following a targeted operation against drug use on a Sydney party boat.

Officers conducted the operation on Saturday morning at King Street Wharf, where the boat was moored, police said.

It is understood prospective passengers were searched at the wharf. Officers from the police transport command, marine area command and the dog squad were involved in the operation, police said.

Two other people were arrested and charged after they were allegedly found in possession of cocaine and MDMA, the pure form of ecstasy. Their genders and ages are not yet known.

A total of 25 people were searched and two cannabis caution notices were issued during the operation, police said.

The 19-year-old man was charged with supplying and possession of a prohibited drug, and was granted bail. He is due to appear in the Downing Centre Local Court on January 14.

Also on Saturday, the drug squad was in the process of dismantling a "large-scale clandestine drug laboratory" on Sydney's northern beaches.

Detectives seized more than 200 kilograms of chemicals believed to be used in the manufacturing of MDMA.

The Warriewood laboratory was discovered following an explosion and subsequent fire on Friday.

On Friday night, four people in the Cronulla area aged between 20 and 22 were taken to Sutherland Hospital having taken what police thought to be a "bad batch" of ecstasy.

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