Last figure I saw was around 20-25% mapped at meaningful resolution. The moon's surface is mapped in higher resolution than most of the ocean floor. That statistic alone should be generating more urgency.
The Seabed 2030 project has updated this significantly - current estimates are closer to 25% at 100m resolution. But resolution matters a lot here. Satellite altimetry gives global coverage but misses features smaller than a few kilometres.
we've sent more people to space than to the deepest parts of the ocean. think about that.