After trying the sink/float experiment, I decided to involve Katrina (my 11 month old) in the process next time.
It wasn't long before the next time & Katrina LOVED it! She stayed interested just as long as Talia did, and even ended up climbing right in at the end! :)
This time since we weren't doing the sink/float experiment, I filled the tub with kitchen items and toys that are fun to use with water (a straw, a rubber duck, measuring cups, etc.)
Another day, Talia used the water tub again, but this time we filled it with soapy, bubbly water.
She loves playing with this tub! Now, if only I could figure out how to keep her from flooding the floor or attempting a spontaneous mini-bath....