To get a full depiction of the bottom contour and composition as well as fish location and depth, I would suggest the F33P. You can hang the transducer over the side or set it inside the hull. Plus, it's battery powered, which is a plus on a tender. http://www.hawkeyeelectronics.com/f33p#!__f33p
If you primarily want to know the depth and temperature, you may want to go with the H22PX. The major advantage of the H22PX is that the transducer is built in, so you wont have a cable to fuss with. It has a fish indicator on it, which will let you know the presence of fish, but is not as detailed as the F33P. http://www.hawkeyeelectronics.com/h22px#!__h22px
If your primary focus will be on fishing I would recommend the F33P.
If your primary focus will be getting the depth & temperature, I would recommend the H22PX.