These are all of the underwater rules I could find. In addition, there are tweets by JC and Sage Advice where it is definitely allowed to cast spells with Verbal components if you can breathe (and maybe allowed even if you can't, but you probably start drowning). The rules are clearly deficient in this area.
The underwater combat rules only apply to weapons, but there may be some parallels.
Underwater Combat (PHB 198)
- Melee
- Creatures with swim speeds are not disadvantaged
- Attacks with daggers, javelins, shortswords, spears and tridents are not disadvantaged
- All other attacks have disadvantage
- Ranged
- All ranged weapons automatically miss beyond their normal range
- Attacks with crossbows, nets (adjacent) and weapons thrown like javelins (e.g., spear, trident, dart) have no disadvantage at normal range
- All other attacks have disadvantage
This is the closest we have to rules about how far you can see underwater. At least we see the recognition that you can't see as far away underwater. There shouldn't be any restrictions based on sight that don't also apply to ranged weapon attacks.
Underwater Visibility & Encounter Distance (DMG 116)
- Clear Water, bright light - 60 ft
- Clear Water, dim light - 30 ft
- Murky water or no light - 10 ft
Water is never defined as an obstruction w.r.t. area of effect spells, but if the DM considers it to be one it should affect all area spells.
A Clear Path to the Target (PHB 204)
If an obstruction is between you and the targeted area, the spell takes effect at the obstruction.
W.r.t. Acid Spash & Ray of Frost, the spell descriptions do not give any support to the idea that they would be diluted during their journey from caster to target, so I don't see any reason to impose that on them. These are magical attacks after all. Even poison spray need not be diminished without a rule saying it should be.
This should ultimately come down to the DM, published adventures (if they are underwater, maybe they will define the rules better), or rule updates. I recommend that you come up with universal rules based on how far/well you can see underwater and refrain from nerfing spells based on their narrative descriptions in the absence of actual rules. It would be one thing to reduce the range of all spells underwater by half across the board, but another to pick and choose how far each spell can work underwater by the fluff in their descriptions. You might also consider imposing disadvantage for spell attacks with somatic components if the caster doesn't have a swim speed. Possibly spells with material components are not possible, but using a spellcasting focus imposes no disadvantage. This all falls under house rules/DM adjudication which you should be able to come to terms with prior to ever running an encounter where the rules are needed.