I have wrote a little program that uses Google Earth as Picasa does for geotagging dive sites (e.g. set their GPS location). It differs from the Diving Log 5.0 built-in feature because, here, you use Google Earth to get the coordinates.
You can retrieve the location by geotagging (the program launches Google Earth and displays a crosshairs plus a little window in the bottom right corner to accept the location or cancel the operation. You can also set the location with the coordinates stored in the Exif. Smartphones, Lumix TZ10/20, and probably other devices add the location where picture are taken.
In the toobar, the KML button creates a .kml or .kmz file with all the dive sites and their descriptions. Save button commits the modifications, and the Undo rollbacks the current site. If you want to cancel all the modifications, close the program and relaunch it.
This tool is an external tool to Diving Log 5.0. The simplest solution it is to confirure it as an external tool call it when needed. With this tool, you can set only some parameters of the dive site (lat, lon, alt, depth, rating and comments). You can not create or delete sites: this must be done in Diving Log 5.0.
Altitude and depth are calculated from Google Eearth: if the altitude of the targetted point is negative, it becomes the depth and altitude is set to 0. It may be a bit hazy, I know

You can download it here : DL5GeoTag.zip. You have to unzip the both files in the directory of your choice (for example C:\Program Files (x86)\Diving Log 5.0\DL5GeoTag) and to launch it at least once. It will display a warning and configure the external tool in Diving Log.
In the project page, you will find how I handled the Earth COMAPI. (Only for interested geeks...)
It requires the .NET Framework 4 Client Profile which has to be downloaded from the Microsoft site : Web install or Standalone install.
And, of course, Google Earth. But, in fact, Google Earth is not essential if you geotag only from jpeg.
THE SOFTWARE IS PROVIDED ""AS IS"", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. And it is not related to Diving Log neither its author.
I have tested on my PC with Windows 7 64-bit Pro and Google Earth 6.0.3.2197.
Maybe this tool will become obsolete one day...

Best regards,
René