Re: Marine Radio
Aside from what was mentioned already, most are built with the circuit boards mounted on rubber stoppers to help absorb the bumps and slams. More expensive than the average car radio (by about 50%), but well worth it in the long run.
On a side note, I bought Sony marine speakers with polypropylene cones and they still degraded after a year. The second set I bought was available with a lifetime warranty for an additional $10 thru West Marine. Worth that money, too.