1. He wants to go to see in the future.

Question

2. He wants to be a seaman in the future.
[Does #1 mean #2?]

3. He wants to go to the sea in the future.
4. He wants to go to the sea (with his family on holidays to rest) in the future.
[Does #3 mean #4?]

Answer 1

If you meant "sea" in #1, then yes, 1 and 2 mean the same thing.

And yes, 3 and 4 mean the same thing. Sometimes, people also say "go to the beach" instead of "go to the sea."