I'd say that's about right on a big tide. Bear in mind I'm a novice sib'er and your boat is bigger than mine!
It's a great place to walk at low tide (sand not mud) to see where the deeper water runs. As you walk towards the sea you will spot a couple of potential hazards. The first is the low tide bridge which is well covered on a decent tide but needs watching at other times. We were out at around high tide the other day but it wasn't a very big tide and I had to flip the engine up to get across!
The second is another small pedestrian bridge by the boathouse of the Fern Pit café. They remove a section of it when the water comes in to allow passage of boats but you need to navigate the supports.
There are occasional swimmers/SUP'ers etc in the river so it needs a nice gentle trickle out to sea. The mouth of the river is generally clearer because the lifeguards herd the swimmers away from the strong current there. It's a little-known but beautiful spot. Enjoy your holiday! I might even spot you out of my window.