channel - An area of deep water that allows large boats to navigate relatively shallow bodies of water (n)

chop - Rough, uneven water, usually caused by the wind (n)

choppy - When the water is uneven due to the wind (the water may form whitecaps when it is choppy) (adj); Antonym: glassy

CID - Cervical immobilization device (n)

close out - A wave that crumbles all at once without maintaining a face, making it difficult to ride (n); what a close out wave does (v)

consent - Permission given by a victim to a rescuer, allowing the rescuer to administer care (n)
CPR Cardiopulmonary resuscitation (n)

crest - The top part of a wave (n); the reaching of a maximum height by a wave (before breaking) or by a tide (v)

curl - The part of the wave that provides a transition between the face and the whitewater; also called the shoulder (n)

current - The movement of the water, either parallel to the beach (a littoral current) or perpendicular to it (a rip current) (n); up to date, as in certifciations (adj)