Boating is the fastest way to slow down - so try doing just that! If you are reading this on a boat then you are already well on your way to that well earned rest.
Relax, take it easy, don’t plan to do too much in a day. Allow some slack time in your schedule for holdups, because there will be some!
Do not cause a breaking wash - this can easily happen in shallow water even at low speed - it erodes banks, reducing depth with the resulting silt, and eventually making boating more difficult for everyone. Be aware that a boat draws water from ahead and the stern goes deeper into the water the faster the speed - reducing the available depth of water and increasing the likelihood of grounding, particularly near the bank.
Passing on-coming boats - Slow down passing on-coming boats because there is less room available for each boat, so less room for error. The movement of water can cause one of the boats (if not both) to end up aground.
Passing moored boats - Slow to tick over (max 2mph) before you pass moored boats - otherwise you may cause the moored boat to rock significantly which is a safety hazard if someone on it is pouring boiling water or using a power tool, for instance. You might also pull out the moored boat’s mooring pins and set it adrift.
Overtaking - It is rare for there to be a need, let alone a safe opportunity, to overtake a slower boat. Best to relax and enjoy the view. If you are consistently being caught by another boat and you don’t wish to increase your own speed, find a suitable straight stretch and slow or stop to enable the other boat to pass safely. Indicate your willingness to be overtaken.