Your idea of the perfect holiday will largely determine which types of sunglasses you should invest in.
If you have a particularly active holiday planned with lots of fishing, boating or SUP-ing on the cards, you'll want to opt for hardier styles of acetate frames (ideally with polarised lenses to reduce glare off of the water) that can survive the inevitable splashes of water, all while safely protecting your eyes from the harsh rays of the Summer sun. We love Oakley's for these types of salty, sunny vacay's.
If lounging around the pool is more your target for down-time, as long as your new sunnies are fully UV protected, you can get away with most frames and styles - provided you protect any metal components from sea and pool water to prevent any corrosion or rusting down the line.
Whatever your style, be sure to pic comfortable, lightweight frames that will make for easy wearing, all Season long.