just went there on this sunday. the location is at 宜蘭, not near 台北車站. It normally takes 1.5 hours by taxi or you drive your own car from taipei to yilan (for one trip and with no traffic jam). So you better give more time for travelling if you really want to travel within one day.
It is within a park, 冬山河親水公園, There are taxi waiting there because it is a famous spot for summer holiday. Or you can ask the service desk within the park to help you to call taxi. the volunteers at the service desk are very nice. But I suggest you can 包車 if you want to ensure the travel time.
other then the lockers, shower, dryer and changing room, there are free chairs, tables and 太陽傘 around the water playing areas. so you can pick your own seat. But of course, you have to get there early in order to get a good location. If you are too late to get there (may be in the afternoon) or it is a peak day (like sat or sunday), you have to test your luck.
other than the water areas, it is a park which you can walk around, the scenes are nice but may be very hot. Other than this, there are shows from different countries. In addition, if you have kids over age 5 and they like the adventure game, there is a rope tower which they can climb and slide, this one must be exciting as kids have to ware helmet for protection. I did not try this as my child is too small but I think it should be fun for some elder kids. it seems that no addition cost for this one as well.You may refer to the official website for more info http://www.yicfff.tw/map