Which beaches or riversides areas In northern ireland are you recommending me to visit in warm summer days?

I like the beach at Portstewart on the north coast. It's like Portrush but a little less trashy. You should also take a trip to Loch Neagh, I was there not so long ago and it was lovely and quiet as the schools aren't off yet. Take your dog there and have a picnic or barbeque!