• Dead Sea is a small circle AoE that has the singular effect of creating flooded water for 3 rounds (increased to 4 rounds at crest level 4 without consumption.) This spell isn't used very often, if at all, due to the low area of coverage, no damage or secondary effects, short duration of tiles (1 extra round is basically next to nothing) while still costing 3 momentum and having another arbitrary cooldown of 3 rounds for a lackluster ability. The only saving grace is that it only costs 1 point to invest in, but Water Dragon pretty much covers its function in every single way. 
  

This directly affects the set up options for spells that rely on flooded water, the most common one being Dancing Water, which in itself is a decent ability. For flooded water Aquamancers, the maintenance of these tiles is often too troublesome to actually use outside of the occasional zoning or unless paired up with another Aquamancer that can help maintain the tiles for you (but often times it's better for them to just use regular damage spells to burst things too.. especially since fights tend to move around.)

• Brine Blade: Target gains 20/40/60% of caster's water attack damage as an on hit water effect for 3 rounds. At crest level 3 or higher consumes 3 crests for a 5 round duration.
  

This was initially bugged when it first came out to use the target's water attack and not the caster's, so I gave it the benefit of the doubt until it got fixed but even after it properly uses the caster's attack it's still... incredibly lackluster (and I'm saying this with a 140 water attack build.) Before level 3 it's pretty much unusable with the low scaling and even at level 3 its damage is easily reduced to negligible amounts with a moderate level of resistance. A base duration of 3 rounds is low enough that it can barely be used before it expires. If you want to extend the duration, it uses 3 crests that could be put towards better spells (or the almighty Crest Break pierce.) 

This (along with other support spells) is also where you will start to clearly see a recurring theme of severe resource inefficiency in comparison to rewards. Let's assume you are casting for the base spell at 0 crests to buff your party early on. That's 9 momentum for Call Storm and 3 momentum for a total of 12 momentum for a low scaling 3 turn duration. If you're a mono aquamancer starting the round with 6 crests? That's still 10 momentum and 6 crests spent for a weak 3 turn buff. Want to extend it to 5 turns as an aqua main with mastery + other sub class? 12 momentum and 3 crests (remember a crest takes 3 momentum to gain on average!) at minimum. 

Along with the previous issues, Brine Blade comes with another arbitrary 3 round cooldown, so you can't even cast it on multiple people as a single target spell if you don't want to spend all that momentum to invoke and buff two people (or, even if it didn't have a cooldown, to spend all those crests on the two spells at higher crest levels.) A possible way to make this spell better is to remove the cooldown and increase the base duration to 5 turns with crest consumption increasing the % scaling of the buff (maybe in addition to a 2 turn duration extend or something along those lines.) This way it isn't completely worthless at lower levels (since you can increase the buff from bad to mediocre scaling with crests) while still giving a solid buff at higher levels (going from mediocre buff to good.)

• Purifying Aquae reduces the duration of the highest level negative status effect by 1/2/3 rounds. At 9 crests, it consumes 6 of them to affect all status affects. 
  
  

• Refreshing Flow gives a 15/30/45 HP regen for 3 rounds with a 7 turn cooldown. At 3 or more crests, it consumes 3 to immediately heal for an amount equal to the regen tick.
  

Another addition to the unnecessary cooldown/too long setup/bad return list, Refreshing Flow has too long of a cooldown for what it does and its crest consumption effect is subpar enough that you don't want to use it. This is the support spell that you generally want to cast regardless of the situation due to it being a heal but most of the time, losing the 3 stack progress towards Crest Break feels like more of a detriment than a benefit to the point that most of the time I find myself wishing it didn't have a crest effect at all. By the time damage takes place and you have a storm up to warrant casting the spell on the whole team, you usually have 3 crests and are forced to use them for the spell. Compare this to pretty much any other AoE healing spell like Healing Discharge, Massed Graft, Malmelo, Cherry Blossom, Phoenix, etc. this is BY FAR the weakest one due to no scaling in combination with a high cooldown. 

Other Call Storm Issues: Hitting higher storm levels is basically never going to happen because on average you'll be spending 2/5 turns of the storm duration casting the extension in itself. It is also overwritten by another Aquamancer casting it, even if their level is lower than yours, so you can't have a team of aquamancers power up a single storm to utilize. The idea of a single Aquamancer on your team using most of their time maintaining for the rest of the party seems funny but for obvious reasons is not optimal or something you ever want to do at all, especially due to the current strength of the support spells it's supposed to enable (maybe if you want to for whatever reason have a flooded water extension bot for tentacles but dark waters already does that better.)

• Water to Wine is fine in itself as a spell but at 5 crests or more consumes 3 crests to add 1 duration to the mist + status effects (you'd usually rather have the 3 crests for Break.)
  
• Water Wall blocks allied projectiles, which can be a hindrance due to its size. If at higher crest levels it could have an effect where it lets ally projectiles pass through, it'd be nice but not necessary as it is good for the investment (not using crests is always a plus too.) 
  
• Ensui Veil is okay as a skill for its fire resist/burn resistance/burn cure at crests levels 6 and higher (the armor buff is basically nonexistent outside of multihits, hence why Ensui's bubble effect is a meme) but has a 3 turn cooldown with a 3 turn duration for no real reason.
  
• Ring of Pearls feels like it should be a support spell compatible with Call Storm (something that might actually be worth the long setup time for to give the entire party the evasion buff.) 
  
• Aquamancer as a whole does not have a way to deal with water immunity/absorb/reflect outside of Dark Authority switching damage to dark type. A skill similar to Verglas' Winter's Bite would be nice.
  
• Aquae Crest and Voyager of Rough Waters both feel like they should be innates once skilled instead of actively taking a skill slot (especially aquae crest since that is the class' whole gimmick.)
  
  

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TLDR: 

• Aquamancers have a huge problem with resource control and generation.
  
• Spells that consume crests often do so while providing little extra benefit and actively delay/decrease power due to losing Crest Break and water attack to the point where it's often better than not to completely ignore using them. 
  
• Many spells have needlessly long cooldowns while having low durations or lackluster effects.
  
• Many spells have setup requirements that are too costly and take too long to be worth what they do.
  
• Flooded water tiles have no maintenance options outside of the very costly Call Storm.
  

This leads to most Aquamancers simply always going straight for 9 crests to get the power spike from Crest Break and abusing the 20/30% elemental pierce with Indignant Idol as a burst mage. 

Since generating crests is impossible outside of using Aquamancer skills, this also locks you out of using other class skills in the turns you spend charging. Since you only get 2 actions per turn on average, it takes a minimum of 5 rounds of using only Aquamancer skills to get back to 9 crests outside of Crest Surge. Other invocations (including future ones for balance issues) further exacerbate this problem by taking 9 momentum in exchange for 1 crest and thusly have to be worth using enough to ignore the lack of crests. 

Aquamancer being marketed as a pseudo-"support" class is invalidated due to having lackluster utility skills with heavy setup and cooldown time while offering nothing outstanding compared to other support classes. A majority of Aquamancer skills feel terrible to cast and feel like they're kept weak and restricted solely to have the Crest/setup system be put to use (and even their crested versions feel mediocre AT BEST.) 

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TLDR;TLDR: crest break water pillar / water dragon / jet stream 3 button aquamancer gameplay stronk unga bunga