396Nova water hunting is a learning experience for sure. My first attempt was about 2 hours also. My arm was killing me but after a few weekends in the water, I graduated to a week at the beach where I actually detected for close to 12 hours one particular day. Now, I did change up some with moving my control unit to my hip (not sure if that is possible with the AT) so if your control head is in the water it will definately add to the resistance of the water when swinging.
Not sure if what I do is proper or not but it works for me, I don't fight the water much trying to power through it swinging, I go really slow and that way I'm not pushing the water as hard which I think allows me to last longer in the water before the arm starts screaming.
As for the 8deep hole, I know it can be done but isn't easy cause as you found out they do have a tendency to fill back in. I have had some that I had to give up on never finding the prize in the hole.... I left envisioning a bottle cap with fins that would just swim off to the side each time I'd dig... it can be frustrating but oh the feeling when you see that yellow ring in the bottom of the scoop. I dig everything, that gold could be anywhere on the scale on a detector so I don't take a chance.
Oh, I tried my waders this past weekend and found that I need something different or larger ones, I could hardly pick up my leg enough to put my foot on the scoop to dig... had to laugh at myself at that one....I need some newer neoprene ones instead of the old style I have that leak also.
Cliff