It's a small park, with mostly children's attractions. The gigantic Ferris wheel is the real money maker of the park, with the other rides seemingly added only to fill up the space. The wheel is so large and the park is so small, that if it was laid flat, the wheel probably would take up more area than the rest of the park!
Overall, this place is probably not worth the trip for anyone with children over the age of 5 or 6, though the Ferris wheel, shooting game, and Zombie Panic might be great attractions on a date along with some other area attractions.
Don't expect food here either, though a couple small stands had some quick treats. The mall just across the street has plenty of offerings in its food court and if I had more time I would have tried one of them. Admission is free, with rides ranging from 300 yen (including the coaster) to 700 yen (the Ferris wheel). The small coin-operated rides are cheaper. There is a free pass available (2200 yen for adults, 1200 yen for children) but there are a couple limitations.
Nagoya Sea Train Land has varied hours based on the day of the week and season, opening at 10:00 or 12:00, closing any time between 19:00 and 22:00; they also close some days. View the park's website (in Japanese) for details (here is the calendar with park hours).