As vacation essentials go, the perfect summer watch ranks right up there with your choicest sandals, sunglasses, and swim trunks. Not unlike the best fitness watches and the best formal watches, the right summer watch is a carefully calibrated blend of style and function, with a palette that will complement your biggest seasonal fits and a design that’s equally suited to sun and sand as kicking back on a patio. Citizen’s Promaster Dive watch delivers that to a tee, and at less than $250 during Amazon’s Big Spring Sale, you won’t have to blow your whole vacation fund just to get one. Citizen Promaster Dive Eco-Drive Watch The Japanese watchmaker has long been known for timepieces that are sturdy, stylish, and crazy affordable, with top-shelf features like Super Titanium cases and the brand’s famous Eco-Drive light-powered movements. In the past few years, however, they’ve taken things up a notch thanks to drops like the 1970s-inspired Tsuyosa (also on sale!) and their beefier Ecozilla diver (five percent off right now), both of which are deserving of …