Toyama's Matsukawa Park is home to around 500 cherry trees that line the banks of the Matsukawa River. It is also one of Japan's Top 100 Cherry Blossom viewing spots, and a popular way to take in their beauty is via a boat cruise along the river itself.
Admission to the park is free of charge, but there is a fee if you'd like to enjoy one of the river cruises. More details about the river cruise pricing can be found on the official website here.
Feasibly, if you visit Matsukawa Park and also wanted to check out the blossoms at Takaoka Castle Park, you could fit them both into the one day - they're about a 45 minute drive or one hour train trip apart from each other. The best time to enjoy the trees in bloom in the region is typically from early through to mid-April.