Fig. 1. Radio frequency attenuation in water^{[79" target="_self" style="display: inline;">–9]}.

Fig. 2. Attenuation curve at different wavelengths^[10].

Fig. 3. Underwater wireless communication scenario.

Fig. 4. Attenuation curve in the visible region, at increasing water turbidity^[10].

Fig. 5. Simulated received optical power as a function of the link distance at different values of water turbidity. Straight gray line indicates the receiver sensitivity.

Fig. 6. Examples of two experimental setups for underwater demonstrations in the laboratory environment^[28,34].

Fig. 7. (a) Picture of the WHOI optical modem; (b) test node with an optical modem installed on top^[23].

Fig. 8. Experimental setup of the sea-trial measurements (left); scheme of the UOWC modem (right)^[36].

Fig. 9. (a) Scheme of the UOWC modem and (b) picture of one of them. The three layers contain a monitor PD, the LEDs, and the receiver^[34]. (c) Experimental setup of the sea-trial measurements.