This document proposes an intelligent learning-based watermark scheme for outsourced biomedical time series data. The scheme embeds a watermark into biomedical time series data like electrocardiography (ECG) images by modifying the mean of approximation coefficients in the wavelet domain. The watermark extraction process uses support vector data description models trained on the correlation between modified frequency coefficients and the watermark sequence to effectively retrieve the watermark without needing the original watermark. Experimental results on ECG data show that the proposed scheme provides good imperceptibility and robustness against various signal processing techniques and common attacks.