from robin d. gill's fantastic* Rise, Ye Sea Slugs!, a compilation of 1,000 Japanese Haiku on Sea Slugs

because sea slug
has no eyes, the poets
write about them

(eyeless especially seaslug's eyes haiku-in often see)

The Turtle's Translation of a Translation

A sea slug's eyes open
only in Haiku. Slugs
are blind in the water.