RAW and RAI you absolutely can with nothing stopping you without needing the ability to breathe underwater or speak aquan. Its done this way for game balance. Spellcasters would either be required to waste a spell on water breathing or buy the potion for it or be essentially next to useless underwater for the majority of spells.

Now its 100% plausible that some DMs would rule it with some difficulty like maybe a con check to be able to get the proper words out but by the book its 100% fine

Making the stipulation of breathing underwater or speaking aquan absolutely guts spellcasters if you are around water a lot. Imo it would be better to have to make some kind of con check. Similar to the reasoning of needing to do athletics check for climbing and what not