Interesting frequency choice. Whistling is pretty popular as a "selective calling" method over HF SSB marine nets.
8281.2 kHz does fall within the legal 8 MHz marine band allocation 8195 kHz to 8895 kHz 8.195 MHz to 8895 MHz.
Going by the ITU channel plan / band plan, 8282 kHz is the closest "channel" but those are more like guidelines than rules.
8282 kHz is part of the ITU dual use (simplex for ship to ship, duplex or "split" operation for ship to shore radio) channel plan, specifically channel 830 frequency 8282kHz USB 8.282 MHz USB (ship transmit) paired with 8806kHz USB 8.806 MHz USB. For ship to ship purposes, using a single frequency is the common practice, and makes the most sense.
The ITU actually only has a handful of designated simplex frequencies on the MF and HF frequencies:
Most of them are in the 2 MHz and 4 MHz bands. 8MHz band only has 8294 kHz and 8297 kHz, plus numerous frequencies in the shared fixed/mobile allocation 8000 kHz to 8195 kHz sub-band: 8101 kHz to 8191 kHz - much like the 4 MHz simplex frequencies 4000 kHz to 4060 kHz (3 kHz spacing - 4000 kHz USB, 4003 kHz USB, 4006 kHz USB, etc.)
8101 kHz USB
8104 kHz USB
8107 kHz USB
8110 kHz USB
8113 kHz USB
8116 kHz USB
8119 kHz USB
8122 kHz USB
8125 kHz USB
8128 kHz USB
8131 kHz USB
8134 kHz USB
8137 kHz USB
8140 kHz USB
8143 kHz USB
8146 kHz USB
8149 kHz USB
8152 kHz USB
8155 kHz USB
8158 kHz USB
8161 kHz USB
8164 kHz USB
8167 kHz USB
8170 kHz USB
8173 kHz USB
8176 kHz USB
8179 kHz USB
8182 kHz USB
8185 kHz USB
8188 kHz USB
8191 kHz USB