Shipwreck + Mushroom Fields at Spawn
Minecraft Seed: 1619306251181231662
You spawn on a little island, and there is a buried treasure right on that island. There is also a shipwreck right in front of you when you spawn.
You will also find a Mushroom Fields biome located right in the middle of a frozen ocean not too far away.
Also, in the opposite direction, there is an above-ground ocean ruin (savanna), and quite a few desert pyramids.