I've a 22-foot sailboat with a typical VHF marine antenna.
With the advent of AIS (http://en.wikipedia.org/wiki/Automatic_Identification_System
), marine antenna manufacturers are now making "wideband" antennas (http://www.shakespeare-marine.com/antennas.asp?antenna=5215
) to accommodate this new functionality.
Conventional wisdom seems to be that boaters can use a 2m radio with a marine (156-162 Mhz) antenna, relying on the loss inherent in the length of coax to handle the mismatch.
I've not used my current antenna for 2m, but had given it serious consideration. Another alternative was to build my own wideband or multiband antenna. However, I was thinking that these new AIS antennas might be a better solution given the price (about $40 retail) and "wideband" designation.