I took the amazingly cool Cellular Bowl design by Shapespeare, flipped it upside down and added a couple things to make it an aquatic creature. I had some 1/2in (or 12.7mm) acrylic tube in the garage I used for the center post but You could print a clear hollow cylinder of that diameter too (4 shells, no infill). Then I used this
LED Module https://www.amazon.com/gp/product/B00INIIJLI/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Left the bottom half of that off, drilled a hole in the side of that and the printed base to run the cord in and soldered in one of these to the battery terminals
USB Cords https://www.amazon.com/gp/product/B01222EM7A/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 for power. Then used misc beads (I used clear iridescent glass beads) on clear nylon string for the tentacles. I used a piece of wire coat hanger in the shape of a circle with a line through it to create the hoop at the top (under the jellyfish shell) with the line through one of the holes in the top mount. That created a nice hoop to hang the beads from. But you could use the 4 holes to run string through to make loops to hang them from as well. Then printed a diffuser lens with 20% infill to help soften the light. Note that the base base has small notches in it to help center the lower mount when you glue it.
Here is the youtube: https://www.youtube.com/watch?v=QrHsd19TMGY
let me know if I can help answer questions