What is the physical appearance of an 'Isolated Danger Mark' (Marca de Peligro Aislado) erected over a small submerged reef?

1. Black with one or more red horizontal bands, and two black spheres mounted vertically as a topmark
2. Solid red pillar with a single black cone pointing down
3. Yellow and black vertical stripes with a cross topmark
4. Green and white checkerboard pattern with a flag