Searchers have been searching the water off San Francisco after a distress call from the couple, their 4-year-old child and the child's cousin, younger than 8, CNN reported.
Cmdr. Don Montoro said the search has cost several hundred thousand dollars since it started.
Montoro said Coast Guard officials will look at the incident and "prosecute it and investigate it to the best of their ability. We're not investigating it directly as a hoax, but we are pursuing every avenue. It's certainly a possibility."
The Coast Guard has been offering a $3,000 reward since last June for information leading to the arrest and prosecution of those responsible for an apparent hoax that set off a massive rescue effort off the New Jersey coast.