it's called a chart. Nautical maps are referred to as "Charts".
nautical
A nautical chart (map) shows the shore and land-marks, sea bed conditions, navigation hazards, buoyed channels, and so on, relating to the safe navigation of vessels and inshore boats.
That mean the key for North, South, East, or West
usually different terrain or height above sea level
Nautical chart
Such a map is commonly known as a nautical chart.
water depths and navigational routes
according to my map, its about 3 inches
Marine Chart or Nautical Chart.
See related link for a star map
Water depth.
navigation on water.
Use a chart not a map. WGS 84 is probably the best datum
The word nautical miles are frequently used by mariners, seafarers, a measure of distance on a geographic map and standard of measure S.I.
it's called a chart. Nautical maps are referred to as "Charts".
In this context, a minute is 1/60 of a degree.