Well seamen boost all the sailors on your ship by 5-6% based on the base stats of said seamen.
First off however:
Whats your CV Crew look like, Each pilot's level, base fighter or bomber stat, weither its boosted and number of vets and experts.
If you plan on doing heavy fighter work, then yeah, a seaman or 2 would be a great asset to add to your crew.
For a CV, your seamen will want to have,
High Fighter followed by High Potential or an Elite Potential or Elite fighter.
IF you roll one, getting a good rep and restore stat ontop of the Fighter and potential (But make sure those are at least 13+ potential and 11+ Fighter)
Personally, I have 3 seamen and I enjoy killing T3s/ occasional T4 fighters with my lvl 72 T2s, but my pilots and seamen are all b/v/ed and I plan on getting 150 more vets on everything. So ask yourself the question, how much am I willing to spend/play during drop events to destroy the skies?
If your looking low budget get 1 or 2 seamen. Just get the natural vets on them and enjoy the 2.5-3% boost they'll give.