buoy

nouns

bright-colored; a float attached by rope to the seabed to mark channels in a harbor or underwater hazards
buoy
is a type of (narrower)
an indicator that orients you generally
"it is used as a reference for comparing the heating and the electrical energy involved"
point of reference, reference, reference point

verbs

float on the surface of water
buoy
is derived from
buoyant
is a type of (narrower)
be afloat either on or below a liquid surface and not sink to the bottom
float, swim
keep afloat
"The life vest buoyed him up"
buoy, buoy up
is derived from
buoyant
mark with a buoy
buoy
is a type of (narrower)
designate as if by a mark
"This sign marks the border"
mark