Complex sentence: A rip current, commonly referred to simply as a rip or by the misnomer rip tide, is a strong channel of water flowing seaward from near the shore, typically through the surf line.
Split into simpler sentences: A rip current, commonly referred to simply as a rip, or by the misnomer rip tide, is a current or flow within a larger body of water. Specifically it is a strong localized current that moves directly away from the shore, typically through the surf line.