My 5.0 Gi/DP VOLVO lost oil into bilge area.

Went out yesterday Fishing & motor starting running rough. Looked at oil gage was at Zero. Stopped motor. Lifted cover. All my oil was in the Bilge area under engine. Dip stick was dry with no oil. Engine will not start. Im afraid thats it for my motor. It had only 78 hrs. on motor. Im sick to my stomach. Can anybody tell me how this happened? & yes the Motor had oil before i went out. Just went over the whole boat. First trip this year. Never had any problems with this motor before this. It ran great.Temperature was normal.

Ayuh,..... You provide absolutely no clues, so I'll guess the oil pan rusted through,......

Or if you had a remote oil filter set up one of the lines could have failed...

You may have lucked out with the engine. You provide little data about the engine, so... these are just SWAGs.
For example, if engine has an electric fuel pump, low/no oil pressure would stop the fuel pump, but engine will run rough for a few secs before stopping. First need to find out how... place to start... who changed the oil last time?
Remove and replace oil filter making sure that you get the seal on the bottom of the oil filter off as well. Check oil filter base for scoring/scratches... cross threading on oil filter center post???... put a thin film of oil on the filter seal with your finger before installing...do not over tighten. Refill with oil and try to restart... ALSO if engine has an oil cooler check it for leaks.

You will need to perform some forensic science.

As Bob mentioned:

rusted out oil pan (although a long shot)
oil filter not properly installed.
leaking remote oil filter hoses.
drain plug not installed correctly.
oil cooler issues, if so equipped.

and yes..... zero oil pressure should have shut down the electric fuel pump.

Dont think volvo uses a fuel pump pressure switch, fuel pump works off the alt
although adding one would be a nice addition