I was just starting a new game (after my brother "accidently" deleted my file and back up)and ui was explloring a bit when i came across the sumereged house to the map south of beregost. does it have any purpose that i never found out or what?

I'm not too sure which house you're referrring to, but I honestly don't know of a single submerged building which has any significance whatsoever. It's just part of the landscape probably.

when i use the question mark it says "a sumereged house. you have no clue how long it has been abandoned". as i said before its in the map directly under bergost.

Then I can cofirm what I just said. That house is completely unimportant.

Maybe slight spoiler

Well actually in the area with all the basilisks, there is a woman turned into stone. If you cast Stone to Flesh on her, she will thank you for freeing her. If you roleplay an evil character you can force her to give you a reward. She then says she has a house near Beregost (slightly to the south of it) and gives it to you. However, there's still nothing you can do with it. ;)
That was your Bit of Useless Information for today, enjoy! :D

When you are in Fieldpost's Inn at Beregost, not far from where Marl's buddy is standing is a bookshelf. Click on this to obtain "The Beregost Real Estate Guide". Read the guide and it will have the following listing:

"New on market. Motivated seller. Beautiful waterfront property and Cape Cod style house. Porch opens directly to water. Enjoy swimming and fishing from your own bedroom. Needs minor repairs. Excellent opportunity for the handyman/handywoman that enjoys a fixer-uppper. Priced to sell."

:D :D :D j/k

That was a joke? Some little s*d in Nashkell sold it to me as a "golden opportunity"! That'll teach me not to play a rogue more often, 'cause I would've known a con when I saw one.

I'm off to sell it to Garrick. He's gullible. For a Bard. ;)