In specific conditions, such as the java seed 6574896947626933751, the spawn selector allows the world spawn to be in open ocean instead of trying to find land somewhere else. This is in the latest version and I'm not sure when the earliest version was.
MC-312264
World spawn selector can sometimes allow the spawn a player directly into the ocean.
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Another seed that seems to reproduce this is the seed 6574897839399958644. It also spawns the player into the ocean due to selecting a spot that has no land.