Ball Under and Out-of-Bounds

I have two situations that I may very well be over-thinking.  

Having re-read the Minor Fouls lesson on ball under, I am still not quite sure how to implement it.  At the level of water polo I officiate, I often see the classic situation on the perimeter in which the attacker has his hand on top of the ball, and the defender lunges, puts his hand on top of the attacker's, and forces the ball underwater.  Rather than let go of the ball immediately, the attacker keeps the ball under for several seconds.  

Although picking the ball up on top is poor water polo, I do not think the action of the attacker is so bad that his team should not only lose possession but also likely be at numerical and/or positional inferiority going the other way.  Of course, the way this is almost always whistled, and the way coaches and players expect it to be whistled, is a whistle as soon as the ball goes under.

If I am trying to reduce the whistling of contra fouls, and I run into this situation--the ball is being held underwater for several seconds--is there any possible response other than whistling the contra foul?  Is the key to whistle before the ball goes under, or as the ball goes under?  Yet, how can I whistle if the attacker has his hand on the ball?  Or is it possible for the attacker to have his hand on the ball but no possibility to play it since his hand is being held underwater.  

The second situation involves inadvertent contact with ball on the part of the goalkeeper.  An attacker shoots the ball.  It hits the crossbar, hits the back of the goalkeeper, and goes into the goal.  That is a goal but credited to whom?  Now, consider the same situation except that rather than go into the goal after a ricochet off the goalkeeper, the ball lands on the water and drifts across the goal line outside the goal posts.  The goalkeeper was the last person to touch the ball before it went over the goal line, so it is a corner throw, yet the inadvertent contact with the ball does not necessarily seem to warrant a new 30-second possession in the half-court for the attack.

Thanks,

David