Speed limits aren't just in place because of Mudflats and wildlife, it's there to stop idiots from causing too much damage to themselfs and innocent others.
I think that 10 knotts is a better speed providing you're curtious with your wake.
Cowes Harbour Master caught me making too bigga wake, blue flashing lights and lots of shouting......I was looking for this guy to appear on the pontoons by the chain ferry. When he did appear this guy indicated where he wanted me to dock and as I rounded the pontoon I was met head on by this "S£^$ty" Harbour Master once again, comming off his mooring. I stuck her into reverse and outboard stalled

. I leant down to switch Ignition back on and key had fallen out

....By the time I'd pulled the key up and inserted it into the Ignition and started the outboard, I looked up just as Kohaku bounced off the side of the Harbour Masters Launch (very gently)

. I just remember this guy nodding his head side to side and tutting.
Ha the good old days

.