If you slow down suddenly, turn, or go astern while you have the dinghy on a long tow-line, you will come into contact with the dinghy and the dinghy tow rope will foul the propeller shaft. The damage can be significant and can spoil your holiday.
Beware of the dinghys’ metal leading edge damaging the transoms when embarking or disembarking your boat. Best practice is to bring the dinghy alongside or in between the hulls on catamarans.