Mountain View-based Google said Thursday that it has rolled out a stock options swap plan, to help the firm's employees--whose options, for the most part, are worth less than the current market price of its common stock. The firm said that at about 85% of the firm's employees have some stock options that are underwater, and that it would look to help those employees exchange those options for new shares. According to Google, the firm's option exchange program will allow its employees to exchange part or all of their existing option grants; the new options will add 12 months to an employee's original vesting schedule; however, no options will vest sooner than 6 months after the exchange program ends. Google said it will take a charge of around $460M over the vesting period of the new options. Google's offer to exchange options is not a new strategy; employee option exchange were very popular in the wake of the dot com meltdown, when thousands of companies did options swap to try to retain their employees.