that's a tough one Chuck, so looking at the surfboard there is a blue 'sperm tail' shape over the white with a thin black border ?
Either way you have a truckload of masking to do, and it has to be done right or the paint will seep under the tape.
Is it worth considering get a signwriter to print the shape in adhesive vinyl ?
The hardest part will be the thin black border next to the blue.