If I get a technician license, am I allowed to transmit on the Marine bands, (of course, legitimate boat related stuff) or do I also need to get a separate permit?
A tech license is only applicable to frequencies within the ham bands. If you are a small craft ship station (pleasure craft, etc.) then you may transmit on the marine band (156mhz to 162mhz) with a part 80 approved radio without obtaining a license. It is considered "license by rule".
I hope this helps. Keep in mind, many boaters also have ham radios on board and a ham license is needed for them. There are a number of HF nets that run that are geared toward marine craft. There is a maritime net at 14.300mhz. Of course, you'd need a general or higher ham license to transmit on that one.