I play Pentoshi when my opponent have no cards, when I'm behind on board or when I have very strong plays. For example I want to play Tywin & Tyrion.
I don't want to play Pentoshi after a Wildfire or First Snow. I want to play it to catch up on boards and then reset their flooding with Wildifre or First Snow.
I have been wanting to put Naval in for a long time. I love Naval and Iniative is very important in second edition. There are a few turns where it shines:
1. I setup Tywin ---> Naval
2. First Snow ---> Naval
3. I kill an important char ---> Naval
I think Naval is great not only in the first turn but whenever you have an advantage and want to lock down the game. Also if I "miss" with Naval I still have 2+ gold for Hear me Roar, it's no problem for me.
Another alternative is Clash of Kings or Second Marched or Winds of Winter, they are all good choices.