This map is an equi-area projection of the Earth with the antipodal earth superimposed. Using this map, I compute that 3.29% of the Earth's diameters connect land to land; 49.33% connect land to water, and 47.38% connect water to water. Total water here is 72.04%.
Below is another map, built from a different starting image. Here total water was 69.02%, probably due to water sections not handled properly by my software, e.g. the islanded strip between Australia and New Guinea.