A new quality of life feature is being tested on the Dragonflight Beta: A NPC that tells you exactly how long until a boat or zeppelin arrives!
To get to the Dragon Isles before arriving in Valdrakken and enabling the capital portal, players must take the a boat/airship from Stormwind Harbor/Bladefist Bay. A problem that is unfortunately common is that players have no real notion of when a boat or zeppelin is arriving.