So, if I could pilot and rent/have a water plane, are there facilities in harbours to let me park?
Yes, lots of them in fact. For what you're talking about the term is 'moor', and there are three kinds of moorings in the vernacular: dock, ramp, and beach. Docking is the most common, beach is the simplest but are hard to find. Landings with a ramp allow the craft to be towed on to land for transport or storage.
Also, it's more complex than simply mooring an aircraft, for any given water landing spot you need to consider what type of fuel can be purchased there (auto or jet or 100 low-lead).
There's also practical considerations about the facilities at a water landing spot vis-a-vis the type of trip you are planning: you can't carry lots of stuff on board an SLSA, so there's the availability of food and lodging to consider. This image shows the basic size of what you can expect to rent...
Source: Pilot Magazine, March 2015 issue, fair use
You mentioned Vancouver, so you'll need to consider which spot has a US or Canadian customs operation if you enter their air space.
Finally, note that maybe a third to a half the water landings in that region (BC and Washington State) are not reachable by public road (that's part of the fun, right?). So there's a logistical factor in effecting a mid-holiday rendez-vous with your friends. Odds are you'll be flying a two-seater so as the pilot, you will spend a lot of time in "
pick 'em up put 'em down" mode.
Are boat spots compatible with water planes and therefore any harbour would be fine?
No, decidedly not. The whole sport is a den of snakes where regulations are concerned. The spot needs to clear regulatory hurdles (e.g., it needs 1k - 1.5k feet for landing), and some boat owners are aggressive about the increased noise of landing and take off and insist upon segregation. Some spots may require more than a simple logbook endorsement. Natural lake spots are the simplest, coastal tide landing spots are the most complex (like avoiding salt water in the cockpit). Some locales have a 'field director' (an unofficial guru) who can give you specifics.
Further research: I recommend 'Powered Sport Magazine' and 'Light Aviation Magazine'. The Light Aircraft Association has a Facebook page, but for anything worthwhile you need to get behind paywalls.
Good terms for Google research are...
- Water Landing Directory
- SLSA aircraft
- LSA aircraft
For a cheaper alternative, consider Short Takeoff Landing (STOL) craft, the image below illustrates an STOL moored by the water in rough terrain. Two seaters with STOL capability are available.
Source: Aviators Hot Line Magazine, May 2015, fair use