4) Spells2.xls in attachment on this thread is a spreadsheet of spells, including the "Special" attribute:
http://www.shrapnelcommunity.com/thr...&Number=500776
If "Special" does not include the "underwater" 8388608 bit flag value (or the underwater only flag, but that should be obvious), then it cannot be cast at/in/on/from underwater provinces.