When there are two maps that meet up at a water point I think it would be helpful if there was a water based equivalent to the vapor portals we transit map to map with.
The entire point where the two maps meet could have a line of bubbling misty water that becomes visible as the player approaches it. When hitting it anywhere along that connection line sends the player to the next map.
A good example is the water based intersection of the Straights of Devastation and Siren's Landing. If the player has the LWS3 map unlocked they could cross that water zone. If they don't then they wouldn't see anything, the map would just get the strong current message and bounce back. It would also be nice if crossing from map to map would keep the player on the mount if they are currently mounted.
I've always wanted Claw Island to be it's own map but expanded to include the adjacent islands. With a water portal players could cross from Sanctum Harbor in LA to Sorrow's Bay back and forth.