Situations like this can get more complicated with cats because the boats can be travelling at very different speeds. In this case the red boat will probably be travelling a lot slower than the others and if the blue boat was any lower she could be travelling faster than green.

Sometimes this could cause a boat like blue to get to the mark ahead of red then just forget all about giving red mark-room. Then if blue does a bad rounding and parks at the mark red could be forced to go outside blue. Blue should take a penalty in that case.