WELLINGTON (Reuters) - The owners of a ship which smashed into a reef off a popular New Zealand holiday spot, causing the country's worst environmental disaster in decades, pleaded guilty to causing marine pollution and were fined on Friday. Daina Shipping, a unit of Greece's Costamare Inc., pleaded guilty to a charge of releasing harmful substances into the sea after its 47,230-ton Liberian-flagged Rena grounded on a reef a year ago. The company was fined NZ$300,000 ($246,000), half the maximum penalty it could have paid. ...