Tips for naval battles

I’m a 3rd or 4th year DM running his second campaign, and in this campaign a prince sent them to guard cargo heading to a dwarven industrial kingdom. They lost their main iron-side cargo vessel due to a Daern’s instant fortress, but have a fleet protecting it to carry the cargo. Next session (I don’t know when the next session will be due to conflicting schedules), I plan on having a large pirate navy attack them for their loot (also gives me an excuse to use a pirate voice). The players are level 5 and this will be each of theirs first naval battle, this is my second but I was a player for the first one. Any tips on both balancing and running the combat would be greatly appreciated.