The first semi-final has the Art Attack taking on the cocky Young Guns in a watery challenge. The teams must build a diving device to send their diving certified expert to the bottom of a "shark tank". While on the bottom they must open a locked box, fill a bag with the treasure in the box and send the bag to the surface. No engines allowed to drive their pumps (which also are hand built).

Both teams are using a diving helmet but the difference is in the pump. Each teams' pump must produce more than 10 pounds per square inch (psi) of air because, at 20 feet, air is compressed.

The Young Guns are going to build a compressed air, or piston, pump. A disc will be pushed down a tube, forcing the air down the hose to the diver. On the upstroke, a valve will open, allowing air into the pump. Repeat until the challenge is over. Up, down, up, down. The disc will be sealed with leather to keep most (if not all) of the air in the hose.

The Art Attack are going for a radical design change on a bellows system. They will stretch and compress small tires to pump air into their helmet. When the tire is stretched up (horizontally) it will fill with air, via a valve in the bottom.  When they squish the tire, the air inside will flow into the hose. Their seal will be crucial.
 
 
 

The Art Attacks expert is Greg Brian	Helping out The Young Guns is Bob Kirby
This is the locked box the teams must open	Art Attack make a cut
The Young Guns aren't sure what to do next	Apparently, some close work is required
Judging todays build is Phil Newton	Done already?
The facemask is welded onto their helmet	Are those little tires up to the challenge?
This cylinder is the crux of the Guns' pumping system	How's the fit?