Hi,

Its model number is ARB2217CSL

I found two...
ARB2217CSL-PARB2217CS0
ARB2217CSL-PARB2217CS2

It's accumulating water in the bottom of the freezer

Certainly -sounds- like a restricted defrost drain.

I can't find out where the defrost drain is to
check.

The defrost drain starts behind the back wall inside the
freezer...under the cooling coils...drips onto a trough there and goes
through the floor and down a tube/hose and into a pan under the
refrigerator. A wire or cable can often be used to run through the hose
to clean it out, or even a turley baster filled with hot water can be
used to blast some water down the drain to help flush it out.

These may help....
http://tinyurl.com/3smnh

jeff.
Appliance Repair Aid
http://www.applianceaid.com/