In general I like CB with SSB capabilities for enhanced privacy. If you plan on using marine radio then keep in mind that it is illegal to use it unless it's on the water. Also, marine band range is going to be much shorter on land than over water. .FRS and GMRS are a good choice for close communications (also, their shorter range could actuallly ENHANCE security). GMRS reallly just adds extra channels to FRS (and those channels require that you purchase a license - no testing required).
MURS radios are not a bad idea, and should be worth checking into.
If close-in COMSEC is the driving consideration then I recommend looking into the frequency-hopping TSX300 model hand-held tranceivers by TriSquare.
Keep in mind that the ubiquitous nature of CB can be as much an advantage as a disadvantage (for enhanced situational awareness). This is one reason I really like CB with the SSB feature. One downside might be that any hand-held units probably have long, unwieldy antennas.