The DHS boat from BW will leave BW, head across to YC/BC, then over to S/D, finally heading down the canal to DHS. The stops are reversed when returning.
My friend and I left Epcot, via the International Gateway, hoping to get the boat over to DHS. It was just heading out....the CMs yelled that there would be another boat in about 15 mins. WE yelled back we would walk and beat them to DHS. Yeah, right...was their snappy comeback. So, off we trekked. The boat beat us to BW by about 45 seconds, but as my friend and I headed to the Luna Park (pool area) of BW, the boat was just heading over to YC/BC. We cut through the pool area, as we always do, turned left and headed down the walkway, along the canal. We didn't see that boat again until we were headed to bag check...and the boat was just coming around the bend of the canal....still about 2 mins out from the DHS dock. I would assume that we were entering the park as the boat occupants got off the boat.
It takes the boat about 20 mins from BW to DHS. You can walk it in 13 mins, but you're moving...not something I recommend unless absolutely necessary!!! A more normal pace will take you about 17-18 mins...that is our normal, leisurely pace.
If the boat is there, and loading and you don't want to walk, by all means, get on the boat. but, if the boat is pulling away, you are going to have to add on about 15 mins until the next one comes along.