It is leaking from the drive shaft hole....
1. If leaking from the hole in the boat through which the driveshaft tube exits, patch with fibreglass or papier machie.
2. If leaking
through the tube,
the top end of the tube must be lower than the water level outside the boat! You'll have to lengthen till the upper end is above the waterline.
You can however try a simple fix first - just put some grease or vaseline in the tube!
Regards.