A BALLARAT family is all at sea with two members serving in the Royal Australian Navy.
Submariner Peter Martin, 26, is stationed with HMAS Dechaineux while his elder sister Rachael, 28, previously served with HMAS Waller.
Based at HMAS Stirling in Western Australia, HMAS Dechaineux is one of six Collins class submarines providing a formidable element in Australia's defence capability.
After joining the Navy in 1996, Peter retrained for submarine duties in 2000.
But as a highly-trained electronic warfare analyst, the former St Patrick's College student is sworn to secrecy about his work.
"Most of my friends now know not to ask but a few still do," Peter said.
He said life aboard an 80-metre long submarine could be restrictive at the best of times with the 55-strong crew often spending weeks away at sea.
Most Collins-class submarines can reach a diving depth of 200 metres but Peter said the transition from surface to deep sea was remarkably smooth.
"It's actually a lot like being on an aeroplane," he said.
"Once you're under the water, it's very smooth and there's no movement at all.
"As the submarine is so restricted, crew members have to make an effort to get on with the people around them.
"It would be easy to fall out with someone in such a close environment but everyone is really professional."
With space at such a premium, Peter said there was still plenty to do and he rarely experienced boredom.
He said crew members worked six-hour shifts with half the crew resting and half on watch at any time.
"As the submarine is so small, you can't exactly go for a run but I try to stay as fit as I can by doing push-ups," Peter said.
"Sometimes we bring a rowing machine on board but I tend to do a lot of sleeping.
"We can watch movies, there's an X-box on board or you can always read a book.
"The food is also very good as we have a couple of chefs on board."
Peter's father, Graham, said he was very proud to have two children serving in the Australian Royal Navy.
"We try to get all the family around at Christmas and they usually all make it home in time," he said.
"To be honest, I'm really surprised that they both chose to join the Navy.
"All their friends wanted to do other things, but they have always been very sea minded. There must be something in their blood.
"Rachael always seemed more determined to join than Peter and I think it was seeing what she was doing that helped him eventually decide to change to submarines."