Favorite way to make simoleons?

I have a couple buddies living a very laid back life at Mua Pel'am on Sulani, who've become incredibly wealthy by fizzing coconuts, pineapples and plantains and diving for treasure and seashells. You wouldn't know it by visiting them though, they live inside the remains of a wrecked ship, and do little else aside from tanning, working out, swimming, cruising around on jet skis and flirting with female sims who happen by. (What little that requires electricity is powered by running on upgraded treadmills.) They do throw the occasional wild kava party too.