Sea Magic is a line of Mikimoto pearls that are not of a quality able to carry the actual Mikimoto brand. There are 5 lines in total. They are as follows:
Mikimoto (The high-quality line)
Blue Lagoon
Gordon's Classic collection (this line is only available in 'Gordon's Jewelers'.
Sea Magic (available at a lot of chain-jewelry stores in malls).
Zales Signature Collection (available in Zales Jewelry stores).
The lines that are not Mikimoto are not bad-quality pearls, they are just definitely not high-end Mikimoto, and are usually quite inexpensive. Sea Magic line is a decent pearl, above commercial, but the nacre will not be as thick and the strands are sure to have higher inclusion ratios.