[alexti]

I can see several directions:
- wait for amphibious or undead mercenaries
- call of the wild, which has already been mentioned. You have plenty of nature gems and if you have several mages cast call of the wild on the same province you have good chances to conquer it and then expand from there.
- faerie queen, it's quite far on research tree, but you'll get access to air and the items to let troops enter the sea. This method can be used in combination with call of wild.
- Horde from Hell, you have access to blood and imps are able to conquer indies quite well. But for Pangaea, this method is slower than call of the wild