"And it is He who released [simultaneously] the two seas," meaning: He caused one to flow into the other. "One fresh and sweet," meaning: potable, "and this one is salty and bitter," meaning: briny. "And He placed between them a barrier," meaning: an unseen partition, so that the salty does not overcome the fresh, nor the fresh the salty.

"And a forbidding partition," meaning: a strictly forbidden barrier preventing one of them from overcoming the other.