A gauge gives a driver of a tow vehicle a visual cue that the trailer is at a proper depth within the water to recover a boat onto the trailer. The gauge has a tubular housing with an open bottom with a float connected to a plunger slidably disposed within the housing. As water enters, the float and its attached plunger rise. Either the plunger reaches a transparent section of the housing and aligns with a band to signify proper trailer depth or the plunger depresses either a first switch for proper depth or a second switch for a too deep condition. Depression of the first switch either illuminates a first light to indicate the proper depth condition or has a meter indicate the proper depth condition while depression of the second switch either illuminates a second light to indicate a too deep condition or has a meter so indicate.