If one wishes to settle and defend aquatic, or even coastal, cities in Rising Tide, a strong navy is essential. While terrain obstacles can enable a slightly weaker army, bolstered by city defenses, to fight an effective defensive war, defending against a naval attack requires a powerful navy*. This might make for an interesting change in game dynamics if there was more than one way to create an effective naval defense. Unfortunately, as far as I can tell, there is simply no strategy that can compete with reaching 6-6 and 7-7 hybrid affinity as quickly as possible. Single affinity upgrades- the most relatively apparent alternative to a hybrid path- provide roughly equivalent bonuses but are impossible to reach on the same time scale. While the unit upgrade requirements suggest that 6 points in each of two affinities are equivalent to 11 points in a single affinity (and that 7-7 is equivalent to 12), the fact that tech costs scale and affinity rewards do not means that the former is dramatically easier to achieve. The fact that melee and ranged ships upgrade from level 2 to level 3 at 6 and 7 affinity only compounds this issue. A player at 7-7 has a navy two full levels ahead of a player at 5 affinity or even at a 5-5 hybrid, and it is remarkably easy to build a navy at level two costs and then upgrade it almost immediately to level four). The next alternative might be to fight quality with quantity, building a large enough level three navy, if not to defeat attackers, at least to force them into extended combat within city bombardment range. This would be feasible if the difference between level three and level four ships was a small one, but unfortunately this is not the case. The jump between levels three and four is by far the largest in the naval unit progression, with melee units literally doubling their combat strength and ranged units, in addition to their own strength bonuses**, gaining the game changing abilities to fire at three range or move after attacking (meaning that cities should never have the chance to shoot back, no matter how high their combat strength grows). Such a dramatic jump would be a balance issue even if it were only differentiating affinity 10 from affinity 12, and becoming available at 7-7 it simply makes any other option obsolete. Thus far, Ive focused on alternatives before 7-7, as these are most important when it comes to survival and game balance. From a diversity perspective, though, its equally problematic that the units unlocked at 7-7 remain dominant for the entirety of the game, receiving no further upgrades over the course of the remaining 8 levels needed to win an affinity victory. Unlike on land, where soldier and gunner upgrades remain options but are largely eclipsed by armor, artillery and a broad array of affinity units, patrol and gunboat upgrades may be joined by hover units and by upgraded submarines and carriers, but they are never displaced from their role as the dominant form of fast moving aquatic firepower. For a player hoping to build cities at sea, or even on the coast, any strategy other a rush to 7-7 affinity seems to be a potentially deadly risk. This dramatically strengthens the already powerful incentives to focus on the inner rings of the tech web rather than experimenting with the outer rim, as well as pushing players away from single affinity research paths. Beyond altering affinity progression rates (which would be an excellent idea for a wide variety of other reasons) the most obvious solution would be to raise the requirements for hybrid upgrades to better reflect the costs of gaining affinity points. A unit that upgrades at 10 points in a single affinity should probably upgrade at 7-7 or 8-8 rather than at 6-6. I would also try to smooth out the progression of naval units, perhaps adding an extra step, to limit the power swing from being a single level ahead. And while its less critical for balance, I think it would be an excellent idea to either alter existing affinity units or add new ones in order to give them a role in aquatic warfare. If Rising Tide is heavily focused on naval play, and if offensive war is dramatically more effective on sea than on land, it seems only natural that naval warfare should have the same opportunities for late game affinity and tech progression as land warfare. *This post is based primarily off of my observations in hot seat multiplayer, but I think the reasoning should hold true for any format in which each faction is at least somewhat competent and genuinely trying to win. I do not take into account options based solely around exploiting the AIs stupidity, which, while potentially effective, should not be confused for actual balance in the underlying game. **Im not sure what the exact numbers for ranged units are, as they dont seem to be documented either in the upgrade screen (except when actually upgrading) or in the Civilopedia, but I think the jump is comparable to that for melee units.