Great water hosted in beat up facilities and used by the Japanese version of the trash from the Jersey Shore thanks to beaches that surround it. Tatsu no Yu is not the best anything. It's been used--heavily. Many people come here after a day of swimming to wash off before returning home. On a hot summer day, this place is packed in the evening with all the beach goers.
It's packed for a good reason however, the water here is great. The view is one of Kansai's best: A very close unobstructed view of the Akashi Bridge.
If you can go on a weekday evening on a non-beach day, I totally recommend enjoying the water and view from Tatsu no Yu. During the summer beach season, I would recommend staying away.