A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
if i have more naval as an attacker than my opponent can i declare a naval invasion and target my naval personality not at the battlefield to perform the action
Reaction: After engaging, once per battle, if you are the Attacker and your current army has more Naval cards than the side opposing it, target your Naval Personality: You have the first opportunity to take a Battle action, which must be performed by the targeted Personality.
if i have more naval as an attacker than my opponent can i declare a naval invasion and target my naval personality not at the battlefield to perform the action
Yes you can, the Naval Personality who performs this Reaction need not be at the current battlefield.
Aside: "naval invasion" does not exist any more in CE.