Too much negative associated with Corsair (It's a Pirate!).
Mariner fits in with Tolkien but then people will always be asking where you have parked the Ship and why you are so far from the sea.
Venturer would be a good name but it's only mentioned in Unfinished Tales.
Swashbuckler sounds dashing and daring without seeming malicious or cruel.
If it is a seafaring class it will probably only really fit the races of Men and Elves anyway. Dwarves and Hobbits coming up short yet again.
Cheers
“It's like in the great stories, Mr. Frodo. The ones that really mattered. Full of darkness and danger they were. And sometimes you didn't want to know the end… because how could the end be happy? How could the world go back to the way it was when so much bad had happened? But in the end, it’s only a passing thing… this shadow. Even darkness must pass.”