Discover a Shipwreck.

Use Riptide to give yourself a boost.

Eat nothing but Kelp for 3 days.

Use a Dried Kelp block as fuel in a furnace.

Place four Sea Pickles in one block.

Dye your bed a different color.

Poison a Witch with a Splash Potion.

Use an Elytra to fly through a 1 by 1 gap while moving faster than 40 m/s.

Bounce 30 blocks upward off a Slime Block.

Create and fully power a Beacon.

Gain the trust of an Ocelot.

Create an Iron Golem.