Intermediate 
Cathal Redmond was swimming off the Greek coast and he was sure he had taken some great photos of colourful  sh with his  rst underwater camera. But, when he looked at the results later, the photos were brown and murky. He took the pictures while holding his breath underwater and blamed the limited time he had to set up the shots. All he needed, he thought, was a little more time to photograph the  sh in their natural environment.
He decided to invent something to make that little extra time a reality and the result is his invention of the Express Dive  a re llable air storage device, which is held in the mouth and lets people swim underwater for two minutes. It bridges the gap between snorkelling, with its limitations, and scuba diving, which gives divers the freedom to breathe underwater but requires heavy and expensive gear. The prototype of the invention looks like a combination of a scuba mouthpiece and a water bottle.
I wanted to enable people to do more. So, rather than just go underwater and spend 30 seconds holding their breath, I wanted people to do a little bit more, says Redmond, 27. In 2006, the Irish designer completed a scuba-diving course and loved the feeling of being able to breathe underwater and observe  sh in their natural environment. Less enjoyable, however, was all the equipment he needed
I was very aware of the fact that I had about 50kg of equipment on me and going under the water felt strange when you are used to trying to keep yourself at the surface. It was a very surreal experience, he says. The real problem is that scuba diving is very limiting. Although it allows you to stay underwater for longer, you have to plan your whole day around it. You have 20kg to 50kg of gear with you  you cant be walking on the beach and decide you want to go in. Planning is a very big part of it.
It was during a  nal-year project for his product design degree that Redmond produced the Express Dive. The device has two main parts. When above the surface, the unit sucks in air through a vent in the mouthpiece. The air is compressed through valves and stored in the tank. The tank has a light that  ashes green when it is full. When air is no longer being taken in, the vent shuts off and, as the person dives, air is fed back via the mouthpiece.
The light turns from green to red when the air start to run out. The device can take in enough air for two minutes of diving and takes approximately the same amount of time to re ll. When you put the compressor into the unit with all of the rest of the stuff, the batteries and the electronics, the dif cult thing was to make it small enough so that people could hold it in their mouths, Redmond says.
Redmond says the mouthpiece feels similar to using a snorkel. He compares it to an extension of the lungs in that the user is taking a deep breath and then using it underwater. It is an extension of the bodys ability to store air, he says. The prototype has been tested in parts. Redmond says he has shown that the motor can compress two minutes worth of air into the unit and that the design can be held in the divers mouth.
What he has not yet done is test the device on a diver, fully submerged for two minutes. But, with enough testing, Redmond is con dent he can get a fully working device that will not endanger swimmers underwater. The device will probably cost 280, he says, and it is likely to weigh from 1kg to 3kg depending on the safety features needed.
To anyone who thinks two minutes of air is no more than a very small improvement on snorkelling, Redmond says it could make a big difference underwater. The typical swimmer can hold their breath for about 40 seconds while underwater, he says. Two minutes is not a lot of time but it is a lot longer than that, he says.