The new cyclodepsipeptide carriebowmide (1), which contains two rare amino acids, 3-amino-2-methylhexanoic acid and methionine sulfoxide, was isolated from the fish-deterrent lipophilic extract of the marine cyanobacterium Lyngbya polychroa, collected from the fore reef near the Smithsonian field station at Carrie Bow Cay, Belize. Its planar structure was determined by NMR spectroscopic techniques. The absolute stereochemistry of the hydroxy acid and all α-amino acid-derived units was ascertained by chiral HPLC analysis of the acid hydrolysate. The stereochemistry of the β-amino acid moiety, 3-amino-2-methylhexanoic acid, was established by Marfey analysis of the acid hydrolysate.