His overwhelming emotion is one of joy.
That the former Great Britain bobsleigher is on the shores of the Redgrave Pinsent Rowing Lake in Caversham at all is something he can barely comprehend. In two months, he will be going for gold for Great Britain in the mixed coxed four at the Paralympics alongside James Roe, Pamela Relph, Naomi Riches and cox Lily van den Broecke. As world champions, the expectation will be huge.
Yet nothing is insurmountable after what Smith has been through. Quite simply, he says, sport saved his life. Two years ago, he lay in hospital with a tumour in his spinal cord. Though the operation was successful, he then developed a life-threatening blood clot.
Those were the dark days but now the glint of a gold medal this summer is the light at the end of a long tunnel.
Smith, from Aviemore, never saw himself as a Paralympian; his focus was on the Winter Olympics after he made the Great Britain bobsleigh team as brakeman. By this time, Smith, who had been born with a clubfoot, had already competed at World Championship level in karate and, having turned to athletics, won an East District title at 400 metres.
However, after experiencing difficulty running bends, he moved on to winter sports. But there another blow struck when a back injury ruined his chances of competing at the 2006 Olympics in bobsleigh. Undeterred, he continued his love affair with sport, having a spell as assistant coach to the GB skiing team, working with the likes of Finlay Mickel and Alain and Noel Baxter.
Smith returned to bobsleigh in a bid to make the 2010 Olympic team but he continually broke down in training and he was diagnosed with chronic fatigue. "I was really starting to have problems with my body shutting down and all sorts of strange things going on," he said. "I went to Edinburgh and I was seeing physios when one told me he worked in paralympic sport and said I'd classify. I'd never thought about it before but I went back to Aviemore and knew I'd reached a crossroads as I couldn't bobsleigh any more. I made enquiries and, before I knew it, I was in a boat.
"That decision probably saved my life. The physio found the tumour and sent me for the scan that was to change my life. One of the feelings I had when I was diagnosed was relief. For 10 years, I had no idea what was wrong with me. This answered hundreds of unanswered questions.
"But then the reality sank in when the surgeon said they would have to take the tumour out and when he explained what it involved, it was kind of like 'wow'. When he said they would go in through the front or the back of the neck, I thought the back would be better as you can't really see it, but they had to go through the front."
Though the operation itself was a success, after Smith went home, things took another turn for the worse.
"I lost the ability to speak and couldn't focus on anything." he said. "Slowly I lost the ability in every limb to the point where I could move my right hand but nothing else. At that point, we knew we had to phone the hospital and I was rushed in for more scans which showed a blood clot had formed in the spinal cord.
"I had to have more surgery and when I woke up from that, all I could use initially was my right arm. I couldn't feel my legs and I knew this was going to be tough."
As part of his rehab, Smith built a website (www.davidandrewsmith.net) from his hospital bed to help build up strength in his hands. It gave him the focus he needed to begin the long road to recovery.
"I built the website originally in hospital to let people know back home in Aviemore how I was getting on," he said. "The left hand didn't work at all, it was completely dead. I used my right hand and when my left started to get better, I used my fingers to try to get it going. It started with just one finger and then two. I was in there for a month and it took a week or two before I could use my entire hand.
"As I was learning to walk again, there was a route around the hospital which would take a normal person about 30 seconds but it was a big task for me to get round it. Halfway round was a set of scales and the nurse told me to step on them to see how I was getting on. I just saw the weight coming down and down and I was saying to myself, don't let it go below 80 kilos. I had to sit down for 30 minutes to recover before I could walk back to my room on my walking sticks.
"The lowest point was standing on the scales one day and seeing 79 kilos. As a bobsleigh athlete, I was 110 kilos."
Smith's positive nature then came to the fore, playing a huge role in his battle back to health.
"It may sound crazy, but I just went into it with the mindset that I was preparing for a competition," he said. "I looked at it as a challenge. I knew if I was worrying about it, then I'd be a mess. I couldn't change the cards that I'd been dealt and I just approached every day by saying today I am going to achieve the things I never achieved yesterday.
"I put up a lot of sports photos from the past on my wall to keep me positive and spoke to a lot of friends from different sports which kept me going. I spoke with Finlay Mickel and Noel Baxter from skiing, a lot of the bobsleigh guys and a lot came to visit me.
"It probably helped that the sports I did were pretty reckless. I used to think back and wonder how I ever went down a bobsleigh run at 95 miles an hour with a big tumour in my neck and not realise. In a lot of ways, I'm glad they didn't find it in my early 20s as I would never have done these sports, so I wouldn't change anything."
Smith today trains seven days a week, having only one day off every three weeks. "It's a lot tougher than what my bobsleigh training was," he says. But the hard work is paying off.
"To win the world title was probably the highest point. It was 14 months after surgery and it was the most emotional thing I'd done in my life. I don't think anything else will come close to that moment. It was like winning over everything, it wasn't just a world title, crossing that line was proving a lot to myself.
"There were times during rehab I thought I wasn't going to make it. In hospital, I was always convinced I could do it but there were times, like when I started on a rowing machine for the first time, that it was impossible.
"I was still falling over in the street. I'd get horrible electric shocks through my body and, to this day, I still have lots of central nervous system and autonomic system trouble. I'm fortunate I have a good support system and the physios work on me pretty much on a daily basis."
The main thing Smith has learned from his battles is to take nothing for granted.
"I got to travel the world and compete for my country and see amazing places and meet amazing people but, at the time, you don't realise how lucky you are. Now, if it's a cold, wet horrible morning for training, I just stop, give myself a moment and tell myself how lucky I am."
David Smith was used to overcoming adversity so when a tumour was discovered and life-saving surgery left him only able to move an arm, it was just another challenge to overcome. A year later the former bobsleigher was winning gold at the World Rowing Champion-ships. Roddy Mackenzie reports