Tracking boats

Dear all, I'm new in this topics and I'm not clear about what is the best solution. I want to tracking the movement of paddle boats in a small park lake (15.000 square meter). There are 20 boats, there is a small "island" in the middle of the lake and I want to have a real time tracking of the position of each boat. I don't know if I have to go for an APRS system or a GPS system. I appreciate any suggestion Thank you very much in advance.

Echi

APRS (Amateur Packet Radio System) is a protocol for using a ham radio to transmit data.

GPS (Global positioning system) is a device for locating the specific position of something that the device is attached to.

Should be pretty obvious which you need.