Swan/Dolphin do have bus service to all parks and disney springs, not the water parks. ETA- I think the recommended mode of travel is transferring at Disney Springs which seems silly. If water parks are on the agenda, I would just uber/ride share.
The only major transport difference between S/D buses and Disney buses is at Magic Kingdom. The S/D buses cannot drop you off at the MK bus depot at the park entrance, they will drop you at the TTC. From the TTC, you can take a ferry or monorail, (and, sometimes bus when it's super crowded) to MK. We've stayed a bunch at S/D and it's never been a big deal. We will also sometimes walk to BC/YC and take their bus to MK or pick up a BC/YC bus on the way back. If you do get dropped at TTC, just know depending on the time of day, it may add 10 minutes to your travel time or could be as much as 40 min or more. It just varies. My kids don't love the extra walking necessary so most times we do the monorail and it's never been a big deal but we're not rope droppers or ever really on a strict time schedule.