Dennis, How have you been???
It's been a long time since I had to deal with Vessel tax however if I remember correctly, it's a use tax applied to boats... I'd suggest you write back and tell them you car will sink if you put it in the water.
Not to drift this thread too much, here's my latest DMV story:
2 months ago, I received a renewal notice for my motorhome. Added to the actual registration costs was a $344.00 penalty for not paying on time. I ALWAYS pay as soon as I get the notice however, after doing some research, I discovered that I never received a renewal. I called DMV expecting them to say that it was my responsibility but,,, they confirmed via their computer that I always pay way in advance and, they never sent me a renewal notice so, they removed the penalty. I sent my check to the DMV supervisor I had spoken to and about a week later I get back an "Incomplete Registration" notice indicating that I need a smog check. I called the DMV supervisor that handled my transaction and asked how I get a smog check for my Diesel powered motorhome.
Come to find out, when I purchased the motorhome in 2003, the dealer screwed up and registered it as a gasoline model.
It took about 3 weeks to solve that problem but, I didn't have to pay the penalty so I guess I won that battle.