Some farms have what they call"stock tanks" where the cattle water. Usually the cattle keep the vegetation down, and you can walk to any point on the bank to retrieve a plane. Also, they are not too big. The ones I remember would be good for spot-landing practice. Definitely use the shadow of the plane coming over the bank to judge your landing position.

I wouldn't fly a RED seaplane there if they have a Brahman Bull, tho' :-)