Cessna 172 single pilot reported an near midair collision event during cruise over shoreline.

Attributes
ACN	1738517
Time
Date	202003
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Visual Approach
Flight Plan	None
Aircraft 2
Make Model Name	Helicopter
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Single Pilot
Qualification	Flight Crew Private Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 60 Flight Crew Total 200 Flight Crew Type 120
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 200 Vertical 100

Narrative:

As I was cruising at up the shoreline at 500 ft. Above the water; a us coast guard helicopter coming from the east with a west heading began to descend. As he was at a higher altitude; the high wing of the C-172 I was on did not allow me to spot him till he was descending and crossing into my path from my right side. Since we were on a close collision course I made a right turn descent to avoid. The coast guard helicopter also turned to its right side and then continued its heading and descent to the east until it reached the beaches. I kept flying north.

Original NASA ASRS Text

Title: Cessna 172 Single Pilot reported an NMAC event during cruise over shoreline.

Narrative: As I was cruising at up the shoreline at 500 ft. above the water; a US Coast Guard helicopter coming from the east with a west heading began to descend. As he was at a higher altitude; the high wing of the C-172 I was on did not allow me to spot him till he was descending and crossing into my path from my right side. Since we were on a close collision course I made a right turn descent to avoid. The Coast Guard helicopter also turned to its right side and then continued its heading and descent to the east until it reached the beaches. I kept flying north.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.