Just to add to this – I use an old Hi-8 Sony camera that I’ve put into service for filming underwater at the moment. I’ve got a low-cost BlackMagic Intensity Pro capture card that has the RCA audio and composite connectors on as well as an S-Video input that I use.
Vegas doesn’t (I believe) supporting capturing directly using this so I use a free application called Virtual Dub just to grab either uncompressed or Lagarith encoded AVIs which I then import into Vegas and edit as required.
I haven’t compared this method with the Canopus options, but the quality is fine for my purposes!