What Is "Sea Level" in Minecraft?

Sea level is Y=63 — the Y-coordinate your feet stand on when you're treading water at the surface of an ocean, and the reference height a huge amount of world generation is built around. It hasn't moved since the 1.18 Caves & Cliffs update, which is worth saying plainly because that update changed almost everything else about vertical generation.

The actual number, and why it's quoted two ways

The topmost water block in an ocean sits at Y=62 — everything at Y=62 and below in an ocean biome gets filled in with water during generation. Your player position when swimming at the surface reads Y=63, standing on top of that water column. Both numbers are correct descriptions of the same boundary; "sea level is 63" and "water fills up through 62" are the same fact stated from two different reference points (block position vs. player feet position), not a contradiction.

What 1.18 actually changed (and what it didn't)

The Caves & Cliffs Part II update extended the world's vertical range from 0–256 down to -64–320, giving the game 128 more blocks of total height — deeper caves, taller mountains. Sea level itself was not part of that change. Y=63 was the default before 1.18 and remains the default after it; what moved was how far below and above that fixed point you can go, not the point itself. If you've seen claims that sea level "changed from 62 to 63 after 1.18," that's conflating the always-true dual-reference-point fact above with the genuinely-changed build-height numbers from that update.

What sea level actually drives

• Ocean and beach placement. Biome generation uses Y=63 as the cutoff for where land ends and ocean begins, and beaches form in a narrow band straddling it.
• Cave carving. The noise functions that cut caves reference sea level when deciding how caves behave near the surface versus deep underground.
• Mob spawn rules. Dolphins, squid, drowned, and turtles require open water at or below sea level to spawn — part of why a lake dug above Y=63 behaves differently from a natural ocean for spawning.
• Rain, snow, and weather overlays reference it as part of the height calculations for where precipitation renders.
• Datapack-configurable, but rarely changed. Since 1.16, a world's sea level is technically a configurable value in the chunk generator settings — but the default of 63 is what essentially every survival world, including any Realm or server you haven't deliberately reconfigured, actually uses.

For picking the right depth to mine specific ores relative to sea level, see the Y-Level Mining Guide.

Frequently asked questions

Is Minecraft's sea level Y=62 or Y=63?

Both numbers describe the same boundary. The topmost water block in an ocean is at Y=62, while your player position when swimming at the surface reads Y=63 — sea level is most commonly quoted as Y=63 since that's the height you actually stand at.

Did sea level change in the 1.18 Caves & Cliffs update?

No. 1.18 extended the world's total build range to -64–320, but the default sea level stayed at Y=63 both before and after that update. What changed was how much world exists above and below sea level, not sea level's own value.

Can a world have a different sea level than 63?

Yes, technically — world generation has treated sea level as a configurable chunk-generator setting since 1.16. In practice almost no vanilla world preset or default server configuration changes it, so Y=63 is what you'll encounter unless someone has deliberately edited the generation settings.

Why does sea level matter for mob spawning?

Several water-dependent mobs — dolphins, squid, drowned, turtles — require their spawn location to be at or below sea level in open water. A player-made lake dug above Y=63 won't reliably spawn these mobs the way a natural ocean will, even if it's visually similar.