The Australian Maritime Safety Authority (AMSA) fulfilled its responsibilities by telling Indonesian authorities a boat carrying asylum-seekers was overdue, AMSA's head said.

AMSA chief executive Clive Davidson told the Senate inquiry into the children overboard affair his agency received information from Coastwatch the boat was late and passed it on to Indonesian search and rescue authorities.

The fishing boat sank off Indonesia on October 19 last year, killing 353 people.

But Mr Davidson said AMSA had received no evidence of the boat being in distress.

"Since Coastwatch had felt it was important that information should be provided to us, we equally felt it was important that it should be provided to (Indonesian search and rescue authorities)," he told the inquiry.

"And that in essence is the beginning and end of it."

Mr Davidson said AMSA was told by Coastwatch the boat was potentially late if it had left Indonesia as expected but because there was no evidence of distress there was no need to warn other ships in the area.

"If we were to send a broadcast out to shipping on every overdue notice we get, there would be a continuous unending stream of overdue notices out to shipping all the time, because every single day people are overdue," he said.