Water in spark plug holes

Investigating a misfire today, took the cover off, all 4 plug wells were full of water. The front bolt was missing from the cover, would this explain the water i the wells ? Number 3 was literally full of water.
Changed the plugs as the old ones looked knackered, runs sweetly now. I didn't use the recommended plug as the shop didn't have them and I needed to get it running - do I really need platinum tipped plugs for the old girl ?

Platinum tip if you want them to last 48000 miles as per service sheets

as long as they get me 6 miles a day for the next 2 months that'll do !

water should not be there unless someone has washed the engine down or a hose has gone and put lots of water there. the number one spark plug hole can get oil in it and that is down to a cam cover gasket .

I sprayed degreaser all over the engine bay when I first got the car but I didn't hose it off. Seeing the amount of liquid in the plug holes I don't think it was that.
I've replaced the missing bolt from the cover, hopefully that'll sort it out.

I can not see a bolt in a cover making any difference it is only the TD4 engine that if you leave the drivers side (in England) it lets oil out. water no.

Jet washed my 1.8 once same problem DOH!