Thanx for the feedback all. Aktungbby that is very useful info and interesting read, good to know. As for the extra fuel consumption: Just get your Nav officer to do a max travel distance report whilst surfaced and then again at decks awash at same speed of course and you will notice a reduction of around 1000k give or take (depending on which boat/current speed etc.) at decks awash.
what Ive gathered so far about DECKS AWASH
pros: smaller target, quicker submersion, ? stealth
cons: slight speed reduction, greater fuel consumption, reduced accuracy for deckguns if at all possible (I usually surface the boat for use of deckguns)
Here I guess a poll would be helpful those for and those against travelling enemy waters at decks awash as opposed to just surface cruising.... Or maybe just THOSE WHO DO

and THOSE WHO DONT.