Flight Instructor on training flight with student reported engine power loss due to carburetor icing.

Narrative

Practicing low level Ground Reference Maneuevers (GRM) with student; who was having difficulty due to turbulence over trees and constantly changing reference points. Decided to head out over the coast to find small buoys and islands to do GRMs off of. Flying through small amounts of light sea scud. Did not consider Carb Icing to be a factor. CFI was distracted due to EFB troubleshooting; and Student was focusing outside on reference points. Did not notice sputtering engine until power was significantly reduced. After a 5 second reaction time; immediately ran through check list items and [requested priority] as the A/C was 600 ft. AGL over water. Regained engine power after 10-15 seconds and immediately cancelled [priority request]. Returned to airport with carb heat on and leaned mixture. Carburator icing is a real threat to Lycoming engines. PA-28-140 POH states that Carb Heat should not be applied until signs of carburator icing become apparent. In areas of likely carb ice formation; manufacturer direction should perhaps be ignored and Carb Heat applied regardless. GRM should always be performed over an area that offers survivable landing spots.