Visible light communication (VLC) technology supports high-speed, reliable, flexible, and cost-effective designs which are demanded most of the underwater wireless communication (UWC) systems. Therefore, in this study, a comprehensive and completely adaptive asymmetrically clipped optical-OFDM based underwater VLC system is designed and demonstrated with widely used and commercially available light emitting diodes (LEDs) and photodiodes (PDs). The designed system is evaluated under twelve different test scenarios with varying fundamental system parameters such as sampling rate, modulation technique and order, and coding rates. In the light of experimental results, it is shown that the system is capable of transmitting and receiving the data supporting both QPSK and 16-QAM modulation techniques with sampling rates of 2 Mbps, 5 Mbps, and 10 Mbps. The experimental results also show that bit-error-rate (BER) could still be maintained on the order of 10-6 over 6.5 m long underwater pipeline channel. In addition, the performance analyses of cold white, blue and green LEDs at wavelengths of 430 nm, 470 nm, and 530 nm, respectively, are evaluated and compared. Their advantages and drawbacks are discussed in detail.