Welcome to The Norfolk Broads Forum
This is THE Worlds Largest Forum devoted to the Norfolk Broads, here you can discuss issues about the Norfolk Broads. Or just somewhere to chat with others interested in the Norfolk Broads area.
Sorry I misread your post thinking you were going next Wednesday.
On Wednesday July 22nd low water slack approx 09:30 and high water slack very approximately 6 hours later.
You can get more up to date info closer the time. From the BA website I think BA tide tables forecast approx 30 days. Don't forget the BA times are for Gorleston and you need to add 1 hour for the yacht station and a further 1 1/4 hours for slack water. Here is a link.
You can get tide tables well in advance by Clicking Here. You don't have to add any time using this website for Yarmouth Yacht station but it provides only low water and low water slack figures.