check out the detailed review below. it comes with a suction cup to mount the transducer that you will want to position on the side of the yak so it shoots straight down. no GPS on this unit. it is the most basic unit you can buy.
http://fishfindersadvisor.com/piranhamax-4-pt/
GPS is really nice to have directly on the unit so you are not fumbling with your phone
check out the garmin striker 4..same price point,little smaller screen, suction cup mount, and a kayak hull mount PLUS has GPS
http://fishfindersadvisor.com/striker-4-portable/
i would recommend stopping in a retailer to see which screen size you prefer
