Shore diving in Howe Sound offers several dive site options. Some sites are suitable for casual divers and large groups, with nearby bathroom and change facilities, while some other sites are harder to reach and offer no nearby services or facilities. Most local dive operators will take clients primarily to Whytecliff Park and Porteau Cove, while others such as Vancouver Scuba diving school will also take qualified divers off the beaten path.
When planning our dives, we always refer to the tide tables to try and estimate when underwater conditions will be at their best. In Howe Sound, the best diving is generally around high tide.
We use a couple of data sources to determine the tides for any particular dive day:
Fisheries and Oceans Canada's website: http://www.waterlevels.gc.ca/eng/find/zone/10
Here is some basic information about tides: High and low tides, and spring and neap tides
As for currents in Howe Sound, it appears that there is no published source of information. I've been advised by a publisher of nautical maps used by sail boat operators that the basic assumption is for a maximum 1.0 knot current in Howe Sound. I have found in my experience that Howe Sound weather reports, especially wind forecasts, are a useful reference for surface currents and chop.
It's important to note that the area around Porteau Cove and northwards to Squamish is a microclimate, where conditions can be very different from the Southern end of Howe Sound closer to Lions Bay and Whytecliff Park.