Personally I'd go with a stores ship, but otherwise I agree with you.
If you insist on hiding it I'd just do it out of sight of land and away from major shipping routes. The ocean is a very big place and as countless searches throughout history has shown it can be surprisingly hard to find anything that isn't transmitting.
_________________
“Close” only counts with horseshoes, hand grenades, and tactical nuclear weapons.
That which does not kill me has made a grave tactical error
Worklist
Source Materiel is always welcome.