This is the best time of the year in my opinion. Especially if you're in the mid-atlantic where we've had the most pleasant July I can remember. No humidity, temperate days - it's a fantastic time to be outside with the dogs. We have Labradors (Lily, the black Lab and Tango, the yellow Lab) who love the water.
When we're at Lake Anna in Virginia, it's not unusual for them to spend 8 - 10 hours in the water each day. No naps, no rest - just go, go, go!
And Nemo, our Great Dane/Hound mix is also a water lover. His favorite past-time is racing Tango to the retriever toy - he's taller than Tango, so he very often beats Tango to the object because he can run through the water much further than Tango before he has to actually swim.