If you like the 1000 Islands seed, try to play with this seed. You will spawn in a village on a small island in the middle of the ocean. Nearby you can find ocean ruins (at 40 ~ 104) and a submerged Nether portal (128 ~ 32). There will be 1000 islands around you and the mushroom one, located not far from the spawn. Sea adventures are waiting for you!
How to use 1000 Islands and the Mushroom One seed
Start the Singleplayer mode
Select ‘Create New World’
Then click on ‘More World Options…’
In the ‘Seed for the World generation’ field, enter -5372512880476291004