If this isn't allowed, then I'll delete it.
Disclaimer:Not written by me!
Taken from the FFVIII official guide book, by David Cassady--
Finding the Ship
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Return to Edea's House and speak with Edea. She'll tell you to look for the White SeeD Ship, which is in a hidden location somewhere around the Centra Continent. She'll also give you a letter that will enable you to board the White SeeD ship once you locate it.
(Tip:You can make a little extra Gil with Edea's Letter. Take it to a shop and you can sell it for 125 Gil. It isn't much, but it can help if you're short on cash. Return to Edea's House and speak with Edea again. She'll schold you and then hand over another letter. You can continue to sell her letters and get new ones to your hearts content.)
The White SeeD Ship is hidden in a cove north of Edea's House. Check your map and compare it to the one shown here. The ship isn't tall, so keep you eyes open for its silver sailds and brown body.
You'll notice a chain of islands that somewhat resembles skeletal fingers. You'll find a small channel flowing through the islands on the east side of this land formation. Pass through the channel heading east and immediatly turn south. This is where you'll find the hidden White SeeD Ship.