: Can i put my kayak in my pool before varnishing?

Putting in the water is no problem - its leaving it out in the
sun that requires the varnish. If you get it wet with seawater
or chlorinated water, make sure to rinse it well before drying
out prior to varnishing.

: I want to make shore that it
: has no leaks in it before varnishing.

For what its worth, my Hybrid Cormorant has now had several lake days and
fourteen sea days without seeing varnish, and its about to go to Ireland
for two weeks, still unvarnished. There is a small but persistent leak
somewhere aft, and I've made a number of small changes (to the skeg box
and to the stem) which needed epoxy and glass work which I couldn't have
done so readily if I had varnished her. This is called "commissioning",
where you make minor changes to the design until it works as well as
possible before final finishing work. Its unlikely I'll varnish this boat
until September when she will be entered in the "craft" section of my local
agricultural show :-)

Andy