Yes you just have to pay admission to the park and they have a fishing barge at the marina. There is a fee for that also. I haven't been there in a while so I can't vouch for it right now.
Last I heard a month ago, it was closed because damage from last years rain. Well, not really closed, but broke and floated off! That's what I was told in March, not confirmed, but also heard they're not in a hurry to repair it either.
Edit: Just called and confirmed. They are going to demolish what is left of the marina, so it'll be a few years probably.
Lynn Creek Marina is open on the other side of JP though.