AirAsia Crash Update

From the Singapore Strait Times:
The AirAsia Indonesia plane which went missing with 162 people on board en route for Singapore is likely at the bottom of the sea, Indonesia’s National Search and Rescue Agency chief said on Monday, as a multi-nation search operation resumed for a second day in the Java Sea.
“Based on the coordinates given to us and evaluation that the estimated crash position is in the sea, the hypothesis is the plane is at the bottom of the sea,” Bambang Soelistyo told a press conference. “That’s the preliminary suspicion and it can develop based on the evaluation of the result of our search.”
He said Indonesia did not have “the tools", such as submersible vehicles, required to retrieve the plane from the seabed, but it is reaching out to other countries for help if necessary.
“Due to the lack of technology that we have, I have coordinated with our foreign minister so we will borrow from other countries which have offered. They are the UK, France and US,” he said. 
 
The multi-nation search and locate operation resumed on Monday at  6.00 am (7am Singapore time) for the plane that went missing in the Java Sea after the pilot requested a change in course to avoid bad weather. No distress signal was sent.
Indonesian air force spokesman Hadi Cahyanto said that five aircraft were involved in the search, including two C130 military transport aircraft and a Boeing 737.
“We are focusing the search area in the waters on the eastern and northern part of Belitung island,” he said. "It is cloudy in some parts but still bright,” he added.
Flight QZ8501 went missing on Sunday morning while travelling from Surabaya to Singapore. The plane had 155 passengers and seven crew members. There were 155 Indonesians, one Singaporean, one Malaysian, one French, one British and three South Koreans.
 http://www.straitstimes.com/news/asia/south-east-asia/story/air-asia-flight-bound-singapore-lost-contact-air-traffic-report-2014
While I am not an expert, I have my doubts.
If the plane is under the sea, then why was no distress signal sent- if they are under the sea, that means they were able to glide into sea and then sink.
If they crashed into the sea, there would be debris scattered in the sea and there would be oil slicks.
Sadly, this seems to be another case of a missing aircraft that may never be found.