I have heard many times the wrong interpretation as to where to drop your ball if your ball went into a Water Hazard.
So you’re clear on the rule, read here is Rule 26-1 from USGA Rule Handbook (http://www.usga.org/Rule-Books/Rules-of-Golf/Rule-26/)
26-1. Relief for Ball in Water Hazard
It
is a question of fact whether a ball that has not been found after having been
struck toward a water hazard is in the hazard. In order to apply
this Rule, it must be known or virtually certain that the ball is in the hazard. In the absence of
such knowledge or certainty, the player must proceed under Rule 27-1.
If
a ball is in a water hazard or if it is
known or virtually certain that a ball that has not been found is in a water hazard (whether the
ball lies in water or not), the player may under penalty of one stroke:
a.
Play a ball as nearly as possible at the spot from which the original ball was
last played (see Rule 20-5); or
b.
Drop a ball behind the water hazard, keeping the
point at which the original ball last crossed the margin of the water hazard directly
between the hole and the spot on which
the ball is dropped, with no limit to how far behind the water hazard the ball may
be dropped; or
c. As additional options available only if the
ball last crossed the margin of a lateral water hazard, drop a ball outside
the water hazard within two
club-lengths of and not nearer the hole than (i) the point where the original ball last crossed the margin
of the water hazard or (ii) a point on the
opposite margin of the water hazard equidistant
from the hole.
When
proceeding under this Rule, the player may lift and clean his ball or substitute a ball.
TJ Vasquez