Final answer:
Janelle's position relative to sea level while scuba diving is below sea level at her current depth, and the device she would use is a depth gauge or dive computer, not an altimeter. The pressure increases with depth, affecting buoyancy and air consumption under Boyle's law.
Step-by-step explanation:
The question touches on the concepts of pressure, buoyancy, and the implications these forces have on scuba diving. Janelle's position relative to sea level while scuba diving is below the surface, at the depth she is currently at. An altimeter, which measures altitude, would not be used in scuba diving; instead, a depth gauge or dive computer that shows depth in relation to sea level is used. The pressure increases by 1 atmosphere absolute (ATA) for every 33 feet of saltwater depth. Therefore, the diver's depth gauge would read an increase of 1 ATA plus the 1 ATA from the atmosphere at sea level for every 33 feet they descend.
As Janelle dives deeper, according to Boyle's law, the pressure increases, causing any air-filled spaces to compress. This increased pressure affects the diver's buoyancy and how quickly their air supply is used. To maintain proper buoyancy, a diver uses a buoyancy compensator (BCD) to adjust for the compression and expansion of air as they descend or ascend. Proper understanding and adjustment of these factors are essential for a safe and controlled dive.