Maritime version of "aviation"
seafaring
(mass noun) The practice of regularly traveling by sea.
‘Canadian seafaring is a fraction of what it once was’
Lexico
...and from Merriam_Webster
(noun) the use of the sea for travel or transportation
"On islands spanning from the Taiwan Strait to Polynesia live the Austronesians, best known for their seafaring."
Most words dealing with activities at sea are adjectives, such as maritime, and nautical. There may be other nouns, but I cannot find them.