Read Ardra's letter.
Check your in-game inbox for mail named "Save our skimmers!"   
 

Check around Amnoon Harbor for leads on Sibaha's whereabouts.
Port to Amnoon wp [&BLsKAAA=] in Crystal Oasis & head west. Talk to Dockmaster Jormick.
 

Find the mysterious charr in Desert Highlands.
Port to Brightwater wp [&BJEKAAA=] & head SW. Talk to Kall.
 

Find the "famous water djinn" or speak to someone who knows him.
Talk to Miyani by the Mystic Forge in Lion's Arch, near Trader's Forum wp [&BBAEAAA=].
 

Ask Moshpoipoi quaggan about Sibaha.
Port to Watchful wp [&BH0CAAA=] in Frostgorge Sound & head west, underwater.
Talk to Caretaker Laamaa in the quaggan house.
 

Help defend Moshpoipoi from the icebrood.
Complete the event, "Help Moshpoipoi village guards defend against icebrood".
 

Check back with Caretaker Laamaa.
Go back to the quaggan in the house.
 

Find the "helpful largos" in Whisper Bay.
Port to Murmur wp [&BK8CAAA=] in Malchor's Leap. Talk to Aaminah underwater.
 

Help Aaminah deal with the Risen.
Complete the event, "Drive the Risen krait out of Kahloipoi".
 

Get information from Aaminah.
Return to Aaminah nearby.
 

Search for Sibaha around krait-infested waters in Mount Maelstrom.
Port to Irwin Isle wp [&BNICAAA=] & head north to Restless Deeps PoI.
Sibaha is in a locked cage on the wooden structure.
 

Obtain a cage key from Sibaha's krait captors or from the nearby champion.
Kill the champion SE of the PoI, top of the wooden structure.
 

Free Sibaha from her cage.
Return to Sibaha with the key.
 

Meet Sibaha back in Lion's Arch.
Port to Guild Bluff wp [&BA0EAAA=] & head south.
 

Earn silver placement or better on Sibaha's Advanced Skimmer Course.
Complete the adventure with Silver or Gold! Good luck!