I'm not convinced by that. Sea water would be the logical ballast and I realise you can't have it sloshing about around the crews' feet but I don't think it wo

I'm not convinced by that. Sea water would be the logical ballast and I realise you can't have it sloshing about around the crews' feet but I don't think it would be too difficult to have a system of bags along to hull of the boat connected to a water inlet. When the boat is full of cocaine they would be stowed out of the way and then when the cocaine is taken off they're flooded compensating for the lost mass. Manufacturing plastic bladders with sufficient strength in the jungle might not be possible but I doubt they're all that difficult to purchase. Worst case scenario they're purchased in the US and only installed when the semi-sub collects them from the fast boats.