Tecnam P92 pilot reported an NMAC with a light engine airplane while receiving ATC flight following. ATC pointed out the traffic after it was first observed by reporter.

Narrative

On Day 0; around XA:00 - XB:30pm local time: In a light sport Tecnam P92 Echo (garmin G3x avionics with no traffic advisories available on display). The event occurred during a VFR day training cross country flight along the shoreline from ZZZ to ZZZ1 since there was better weather than the further west side of the National Park (I was present for preflight planning while the student contacted the weather briefer to confirm it to be the best routing). We were using flight following (contact with ATC and on the transponder code assigned). When flying south along the shoreline; it occurred around the area from beach down to [the] channel. We were staying clear and under the Class B. Both my student and I were constantly scanning for traffic and spotted behind us on our right side; a multi engine aircraft(I believe it was a Piper Seneca) pass us really close; it was difficult to tell the exact distance it could have been approximately 100-200 ft horizontally apart from our plane. The Seneca flew south for a few seconds then turned back North bound initially not directly over the shore just over to the inland part. At that moment ATC called to advise us of traffic. I told ATC we had them in sight and that was a close call. That plane was not under any contact with ATC.