Student or Learner
Sailors have special navigation / navigational equipment to help them navigate in the waters.
Which bold word should I use?
***NOT A TEACHER***
Both seem possible to me, as tzfujimino's links also demonstrate.
Navigational equipment. Here "navigational" is an adjective.
Navigation equipment. Here "navigation" is a noun, but it describes another noun. Two different examples of a noun describing another noun are "history teacher" and "race horse". See Noun as Adjective.