I bought this year's edition of L'Eau D'Issey Pour Homme Summer (The one with the seafoam green and white horizontal stripes on the bottle) and have been wearing it on hot days. I like it, along with the original. I think both of these are much better and more unique than Acqua di Gio. The Miyakes have an unusual note of yuzu which gives a Japanese character, also tobacco and vetiver in the base. The original L'Eau D'Issey Pour Homme is more complex and longer lasting than the summer edition, but you want to be careful not to overapply. It's powerful stuff.
The Summer version has netted me some compliments already and I find that it really goes well with the heat. As it dries down, it moves toward a nice fresh vetiver base with a hint of sweetness. The original is still the best and most complex, but the Summer version keeps the parts that work best in the heat and it smells great.
If you want to spend some big bucks, check out Creed's Erolfa. I wore it today and really enjoyed it. Very crisp and oceanic and the longevity is unreal. It's expensive and it smells that way. It's maybe a more mature aquatic scent, but you may like it too.