Used the XIOS Sonar Diving Navigation System the other day. What a neat unit. Shows direction like a compass and the distance to the transmitter up to 3000ft away. Makes using a standard compass boring.

True enough. I started using the NeverLost navigator (for shallow [above 100] reef dives) several years ago.I recommend that, as with computer diving, you make an effort to see the device as convenient, but not entirely reliable. Sonar is affected by reflection and refraction (thermocline and water density factors). When the conditions are ideal, sonar is ideal. When the conditions are not so good, think of sonar as a less than trustworthy advisor...or be ready for a very long surface swim.

So far the reports from divers using the XIOS has been very good. The most common problem seems to be getting the unit ready to use. Read the instruction manual carefully. The unit only works in water. Once you have the set-up procedure completed, the unit will be ready to go. Be careful with handling the units. If you drop the wrist unit it may be damaged. I found using a Pelican 1200 case with foam was a good way to transport and store the units.