You don't mention your interests, so it's difficult to know where to point you - there are more options than you can possibly fit in during one day! Some things to look at:

1. If you have a nice day, then stay outside. Option 1- rent bikes and ride the seawall around Stanley Park, then continue onto the linked path around False Creek through Yaletown, over to Grandville Island and finish up at Kits Pool (bring swimsuits and go for a swim in the pool or the ocean). Option 2 - head over to the north shore mountains for some hiking with spectacular views back across the city. Check out trail options on Mount Seymour or Cypress Mountain (both provincial parks, so see the BC Parks website), or, if you feel like taking on a cardio challenge, hike the Grouse Grind and spend time at Grouse Mountain. Capilano River Regional Park also offers spectacular forested trails over a canyon. The Lynn Canyon Suspension Bridge and associated trails would also be a good destination for you.

2. If its raining, then check out the Vancouver Aquarium, the HR MacMillan Planetarium, the Maritime Museum or the UBC Museum of Anthropology. Wrap up with some shopping along Robson Street or in Pacific Centre.

Consider trading the ferry for the helicopter. Helijet has an advanced booking on line rate of $130 one way. It is a spectacular 35 minute ride and will free up many hours. Ferry and gas will take about six hours return and cost more or less $200 return.http://www.helijet.com/