I think the bus from WL to MK is much faster than the boat, and once you get off the WL bus, you'll be at the bus stop already, instead of having to walk from the boat dock. I would think the bus is much faster too.
From there, I'd hop on a bus to the Swan. This will drop you off at the front of the Swan. From there you walk out the Swan and go across the street. If you aren't sure - just step inside the lobby of the Swan. If it was mid-day, and a bus for the Boardwalk was there instead, I'd consider that, but the walk will be longer. Mid-day waits for buses can be 30 minutes. From the Boardwalk - walk directly to the Swan, it will take about 15 minutes to get to the front of the Swan, assuming you walk in the correct direction.
Of course you could also take a taxi...
You could also take the MGM bus from WL, then then the boat to the Swan, but I think the first would generally be faster. Having stayed at the Swan numerous times, there is not a good way to get from MGM to Fantasia Gardens - there is no cut through. Walking to the SWan would take about 15 minutes from MGM.