There are no Skyblock seeds, you have to make your own. If you are interested in making one you can check out this video:
For survival island, I have 2.. michael jackson 4 president-
It spawns you right off shore of the island. If it doesn't, just go to the middle of the map. This island has a lot of grass and trees. It also spawns alot of passive mobs like pigs, cows, and sheep. This island also has wolves.
I believe it only has 1 tree and a lot of clay and sand. Hardly any dirt. The island is located at x41 z19.