I used an abalone shell for the base, washed it out well, and then plugged the tiny hole on the bottom with plumber's putty. It's holding up well. Added shallow shells face up for some additional water catchment, some broken sticks from a driftwood piece, and some "faux" beach glass. Gave it a place above the basil (now dormant) which is one of the bees' favorite hangouts in Spring.
ETA: Looks like my photos did not upload the first time. Repeating. Also, checked again today and the putty is holding. Pretty sure it's there for good.