Once is enough already....
 

I was recently on patrol and my watch officer sighted a destroyer in the distance....it was dusk and the enemy was moving away at a good clip so I decided to stay surfaced...problem was....my watch crew kept calling out the ship every five seconds......it got real old real fast and I ended up submerging just to get some peace and quiet.....is there a fix for this ? I have encountered this before and seem to remember reading about this also.......Rick

AFAIK, this happens when the enemy ship goes over the "seeing" distance of the watch officer and later on comes back, because it slowed down, turned or something like that, making the WO call it again as it enters his visual range.

As the Ferret says, when the ship is at the limit of the visual range, the officer or lookout will lose sight of the target and regain it. Each time it will report ship spotted.

You could feasibly just remove the watch officer/hydrophone operator and just log the ship yourself.