help!!! fluid machanics in water pool
 

i wanna know how can i make a machine (fans) work perfect under water. i'll discribe the situation, and please tell me how to do the math.

there is a water pool.
long= a meter
wide= b meter
water depth= h meter

we put fan in the centre of the pool, floated. the two rectangle oars
submerged. oars are perpendicular to the horizontal water plane.
area of each oar= s
length of each oar= r

then we let the biofan rotate.
palstance= w

at the same level with oar, water is emited horizontally.
directly under the mechine, water moves frome bottom to the top, because of the subpressure in the centre of rotating.

the problem is we donnot know under what conditions this water movement circle can touch the bottom of water pool.

i wanna know the relationship between h/s/r/w/

please please help me.