Easiest way to drill a hole in a sea shell?

electric drill with fine drill bit.

Dremel with a diamond bit should work, too.

i use my dremel tool with a fine bit.

use a dremel machine and go slowly.

Don't go too fast, go slowly with not too much pressure to help prevent cracking from the hole.

https://www.wikihow.com/Drill-a-Hole-in-a-Seashell-(Without-a-Drill)

I’d recommend running your drill bit in reverse first and see with light pressure if it will still drill thru your shell? Running it backwards your drill bit won’t grab the shell and possibly crack it or worse! There are some round ball like tips that are more of a file rather than a drill bit. Those may work even better in a fragile shell for making a hole! Good luck