to the bottom of the boat referring now to fig4 and 5 means is provided in receptacle 20 for interlocking the tow bar 6 to the receptacle 20 such means may be in the form of a pin 34 which is positioned to engage an l shaped locking groove 30 provided in the bottom end 28 of the tow bar 6 when the bottom end 28 of the tow bar 6 is inserted into the receptacle 20 the vertical portion of the l shaped groove 30 is aligned with the pin 34 in receptacle 20 the tow bar 6 is moved axially to align the pin 34 with the horizontal portion of the groove 30 the tow bar 6 is then rotated in receptacle 20 to lock the pin 34 in the groove 30 to prevent the tow bar 6 from jumping out of the receptacle 20 supporting means for tow bar 6 may optionally include a mounting plate 40 in the form of a flat member 42 as shown in fig1 an aperture 46 is provided in member 42 and has a diameter sufficient to accommodate tow bar 6 the mounting plate 40 is affixed to stern deck 38 or stern wall 36 with the aperture 46 axially aligned with an aperture of the same diameter in stern deck 38 or stern wall 36 in addition the plate 40 includes a.