Tidewater Inc., which provides supply vessels and other services for offshore energy operations, said Friday its board approved spending up to $200 million to buy back shares. The company said it would use available cash and borrowings from its revolving credit facility for the purchases, which could run until June 30, 2009. Tidewater recently completed a share repurchase program, under which it bought back about 4.5 million shares for about $250 million.