If you're selling a product that people can imitate, then intrinsically its not
valuable. If you think there is $500 of material or labor in each and every snorkel then I have a $500 keychain to sell you
I just thought it was poor form for them to come on here and make threats that they couldn't possibly keep - they may think its a little ocean, but legally I suspect they'll find its ENORMOUS. ARB certainly doesn't own a patent on "plastic air sucking devices", and if they have a design patent or trademark on the shape (which, if they do, they're not saying so anywhere on the 'net that I can find) then its certainly not an international instrument.
Honestly, I'm just being cantankerous, as I'm not about to take on another project out of spite. However I can say with certainty now that ARB employs at least one total dick, and they were just trying to intimidate you here.