I don't have a Lagoon but here are some alarms that could sound on my Saba 50 with engine & generator off:
- automatic bilge pump activation - Engine control panel is energized, but engines are off - low battery state-of-charge or low battery voltage - Carbon monoxide detected - anchor alarm set on chartplotter and boat has gone outside the radius setpoint (there are numerous other alarms that can be set on the chartplotter) - AIS proximity alarm triggered - Radar proximity alarm triggered - Man Overboard button pressed on chartplotter - Digital Selective Calling message received on VHF - Chartplotter has lost communication with Autopilot