"That is a very big ship."
Translation:זאת ספינה גדולה מאוד!
In modern usage, אניה is for bigger ships. Officially by the ministry of transportation:
"sira" is up to 7 meters in length. Think kayak, canoe, small boat. Doesn't require a license in Israel.
"sfina" is from 8 to 24 meters in length. Think yacht or amateur fishing boat. Requires a skipper's license to operate
"oniya" is more than 24 meters. Requires a much harder to get license.
Find anybody anywhere who will call this אניה and I'll believe you
That's a סירה in my opinion, it's too small for either ספינה or אנייה.
Just look at google image results for ספינה and אנייה, the results aren't too different in terms of size. You can also check news sites/Wikipedia/internet - they use ספינה for big ships or just use them interchangeably:
You're right, I intended to say it's more frequent in the Bible. "ספינה" is used only once in the Bible, in Book of Jonah, and this is one of the signs the book was written in later times than other biblical books (but I'm no expert, and there are other explanations for the strange use of "ספינה" in Jonah).