If you want to manipulate gravity of course you can use apples. But by hanging eight kilos of apples on to your weight belt you don't have the same result as with eight kilos of lead. As for weight, above water you do, but under water you have to subtract the weight of the water, displaced by the apples. That goes for the lead as well, but that displaces far less water.
Also, to move the volume of the apples causes like ten times more resistance than the same weight in lead. So with that you swim a lot easier. You could call lead the superlative of gravity.
Because lead is over 13 times heavier than water this sometimes opens up unexpected possibilities. But before I go on, a fair warning: cows that licked a gate painted with lead white became stark raving mad and so did the innkeeper who took the first drink that had rested overnight in a lead supply pipe. Lead is poisonous!
When I started diving I thought to take the perfect weight belt to the club. At the scrap yard I got a lot of wheel balance weights, small pieces, from 5 tot 100 grams. That I evenly divided onto a belt. Thus I thought to be perfectly balanced in the water. But when I was handed a weight belt with blocks of 1 and 2 kilos this also worked perfectly. I had precisemised again.
Another adaptation was short-lived as well. I had decided that when walking you move your limbs in a pendulum fashion and was curious to find out what happened if I increased the momentum. Therefore I attached half a kilo of lead to the instep of both my shoes and held the same weights in my hands. With that I walked up and down a bridge. The effect was surprising. Once in motion it felt like enhanced, even up the bridge. But it did tire me more.
Of the following use I unfortunately can't show photographs anymore. As a sculptor I bought the trunk of a meadow oak some twenty years ago. Contrary to forest oaks that grow rather straight towards the light, a meadow oak is more irregular. This trunk had rather a strong curvature and it didn't take long to see an orca in it. That turned out beautifully, the power the fluke flung up as well as aside with was radiant. Just a pity of the wood rot underneath at the chest. Finally I chainsawed, hew and cut it out. Then I melted lead and poured in a total of 80 kilos. Next I installed the orca in my garden on top of a standing tree trunk in such manner that, because the point of balance had shifted so much to the front, it looked as if it came sliding from above, like a 3D trompe l'oeil.
My most recent application of lead dates from three years ago. I had made a waterwing that deviated strongly from the usual half-rounded model. See also 'The Waterwing Museum' on the homepage. This wing was based on the pectoral fins of a Humpback whale and made of double glued, marine, 20 mil plywood. As the wing was rather buoyant, which made it hard to dive with, I mounted lead on it. Initially I felt I would have to apply the weights as far apart as possible, but in test swimming the wing turned out to be hard to manoeuvre. When Dusty suddenly turned up I wanted to get into the water as fast as possible and wrapped in haste a belt with a lead block on it in the middle around the handle of the wing. This worked as a revelation. It made the wing super manoeuvrable. In hindsight it's indeed logical, this way I have to move the least mass.
And this happens to me a lot. Not that I do things pot luck. It's more like taking the error out of trying.