He's shed 10kg of what he terms "blubber", replacing it with 1kg of muscle on his 2m frame.
"It would be much more comfortable to stay indoors," Bridgewater says. "There's no coach out there and no crew to compete against. It's just me and my goal."
The 2005 world champion spent five years devouring an elite circuit which included regattas at Amsterdam, Munich, Lucerne and Poznan. His appetite has returned.
Bridgewater is due home later this year in the hope of representing New Zealand again at the Rio Olympics. He will base himself in the Waikato and, while rowing commitments might intrude, he'll be home more often than on punishing 12-hour days working for financial services firm Morgan Stanley.
"I originally left the sport on my own terms but I was exhausted," he says. "I wanted to do something different. The Oxford MBA programme was perfect. I thought it might be a bit toffee-nosed but it was a great student town full of young people having fun. It's helped open doors.
"After the Boat Race, I wanted to see if the yearning for rowing would return. Watching the guys in London rekindled memories because I was of their ilk and standard and they smashed it. It was exciting to see and, sitting on my sofa at the time, I thought, 'I want to be part of it again'. That kicked things off."
Bridgewater expects to suffer because recovery is tougher now his body has lost conditioning.
"I'm under no illusions it'll be a black hole for the next six months, but it'll be worth it.
"Going back with a young family is probably quite complementary with a couple of kids who can spend more time with Dad at home.
"Fortunately, I've saved some money and, hopefully, I'm not going to have to spend my life savings. I'm in an incredible position to have another crack at a dream [of winning Olympic gold] I've had for 15 years and funding is hardly an issue now with the phenomenal support available to up-and-coming targeted athletes."
Perhaps, surprisingly, work as a trader could pay dividends in Bridgewater's rowing career.
"I came in thinking I'd have to tone down how competitive I am, because I mightn't fit in, but it was almost the opposite," he says. "There were some aggressive characters. I was shocked when I first showed up but you adapt after a while. Those first two years were hard to deal with.
"I had to assimilate from an environment where I was good at what I did. Inevitably you'll make mistakes [in the trading industry] but it's so obvious when you do, because you lose money.
"It's a rollercoaster ride and typically there was a lot of schmoozing with clients afterwards which makes for a glamorous but, at times, tough lifestyle."
