I have an argonian character and i took him just to be able to explore undersea without having a breathing problem.I am planning of searching all the underwater surface but before i do it i wanted to ask if there are any treasures undersea to find.Like fin gleam in Oblivion?Or any unmarked entrances?

As far as I know, there isn't much to find. There are some sunken ships along the northern shore and in lakes you can occasionaly stumble upon a chest, but you'll only find standard loot. No unique items or quests, sadly.

Oh, and one of the treasure maps leads to the bottom of a lake. This could qualify as a quest, I guess.

Not that much. I was a little bumped down when I realised that in an exploration game there is little to explore on the bottom of the sea. Makes sense tho, underwater combat is nonexistent.

I wouldn't know myself. Have a weird fear of descending to great depths in video games. That said, I tend to stay from the water..

There is a shipwreck though..that is really far down below the ocean surface.

Damn!I would love something like the message in the sea of ghosts in morrowind

Me too. In Morrowind I was always underwater exploring, harvesting clams for pearls, entering underwater caves, killing monsters. At least there we could use our weapons. Boethia quest was cool. Reward with Goldbrand was great!! Later in Oblivion there was almost nothing apart the enchanted helmet mentioned above. Now in Skyrim there is nothing to see. A sunken boat in Sea Ghost, another in a lake and some treasures. There are no pearls (they could have put a few oysters with pearls among the clams!!). The only thing valuable is fishing. Cyrodilic Spadetail, River Betty, Abecean Longfin, Histcarp, etc. To kill slaughterfishes we must now use a lot of tricks to attract them near or outside water. I think they put the Bard Leap for the players nostalgic of Morrowind...

I never saw anything special, ship wrecks, a chest or two with nothing special in them and barnacles, clams and fish. The shipwrecks were probably the most interesting, following the trail of ruin as they got deeper into the trench.

Agreed not as much treasure as you would think considering its such a wild coastline but still worth exploring i would say and some of the dungeons/caves have treasures below the surface

Next Elder Scrolls game: insta-death upon entering deep water, like GTA 3!

When I was doing the winterhold questline, and had the collapse explained to me I immediately headed down to sea to see if the ruins were still under the ocean. A missed opportunity I think. That would've been awesome to explore the sunken streets of winterhold.

This is that shipwreck I was talking about. http://www.uesp.net/wiki/File:SR-place-Pilgrims-Trench.jpg

Yes.... Too bad that they didn't do it. The ruins of Winterhold under the Ghosts Sea!! Woah.... Like the ruins of Boethiah Shrine in Morrowind. It was awsome to see them while walking on water or swimming.

I agree. In Morrowind when I first noticed the ruins beneath the water it was kind of eerie. Then spent the time adventuring for the gear to check it out. I do enjoy the northern reaches of skyrim though. To their credit, it was cool to cross the ice flows and find tombs, shipwrecks, and even bandit groups living out among the ice.