Whales breaking the surface close enough to feel the splash. Dolphins racing your bow wave for miles, playing in the pressure wave your hull creates. Phosphorescence trailing behind you at night - bioluminescent plankton turning your wake into liquid starlight.
Weather systems approaching from the horizon like slow-moving architecture. Squall lines you can see coming for hours, dark walls of rain moving across the water. Lightning storms at distance, illuminating cloud structures from within.
Sunrises and sunsets with no land to interrupt them - just color spreading across the entire dome of sky, reflected in water that extends to every horizon. Stars so dense you can navigate by them, constellations wheel overhead with no light pollution.
Islands emerging from haze as you approach. Coastlines seen the way they were meant to be seen - from the perspective they were designed for. Sea caves, offshore rocks, hidden coves that don't exist on any road map.
Other boats - but rarely. Sometimes you'll go days seeing only cargo ships on the horizon. When you encounter other sailors, it's always significant. Shared nods between people who chose the same kind of reality.
And the water itself. Different colors in different depths - the deep blue of open ocean, the green of coastal waters, the startling clarity of tropical shallows where you can see your anchor chain disappearing into sand 30 feet below.
Weather you can taste in the air hours before it arrives.