I'll try and remember to ask the ships crew about those. The translation may be interesting.
Engineering one. 'take off half a gnats c*ck' - reduce something in size by a very small amount.
I think the dog one is similar to "once bitten, twice shy" but three times better.
I was having a laugh with a colleague at work today as we were waiting for a very boring automated test to finish and he told me about one time he was on the toilet and leaned back (presumably in satisfaction at a job well done) and due to the position of the lever, accidentally flushed the toilet while he was still sat on it and gave himself, and I quote, a "Birmingham Bidet" and that his "Sherrif's badge" wasn't expecting it.
I apologise for lowering the tone but that had me in stitches earlier today, never heard either of those terms before. Don't know if they're regional, just slang I've never been in the right company to hear!