How do you get mm-wave radiation to an aquatic plant? Skin depth at that frequency is tiny. Are they doing studies on duckweed? (Look up the plant, indeed, they

How do you get mm-wave radiation to an aquatic plant? Skin depth at that frequency is tiny. Are they doing studies on duckweed? (Look up the plant, indeed, they are.) And I can see how pine needles might be more affected, what with size and pointy tips.