Tide-Line Blue

Both shows are about rebel battleships with interesting crew which main hero joins, set in postapocalyptic future, on a planets which survived environmental disaster and are similar but not quite to the modern earth. Both involve protagonist growing up. 

both are futuristic underwater action/adventure/drama genre. XD 

Most of the land on the Earth is covered with water. Both animes have some kind of terrorists/rebels who are not pleased with the new nations. In Tide-Line Blue the rebels are on the good side and the terrorists in Tactical Roar are on the bad side. Not much of similarity but you may like them both; some of the romance may be similar too. There is also a lot of ecchiness in Tactical Roar that you may dislike.