I wrote this poem in between phone calls when I was working in an insurance company in Pasadena, California, shortly before I moved to Florida.  It remains one of my favorites among my poems.
Obviously, for anyone who has done any boating, the subject is a dolphin; in this case, a Pacific Whitesided Dolphin (Lagenorhynchus obliquidens), which was one of the most common - and beautiful - species common to California.  The dolphin in question was leaping between our boat and the setting sun.

This poem first appeared in a poetry anthology dedicated to California poets, and though unfortunately I do not recall the name, it appeared around 1983 or 1984.