Wrist A Wave is symbolized as one of the strongest forces on earth. So strength for one. Also if you read more into it, its about faith, a wave is you against mother nature, you cannot control it, you just have to put your faith into her.
Essential ASL Sign Language - for SASL (South African SL) please ignore the signs for "good-bye", "thank you" and "later", the other signs are the same. Also the ASL sign for "please" is the SASL sign for "pleasure"