Namora
Before falling in love with the arts and hitting it big as an actress, Katherine Langford’s claim to fame in her home country of Australia was being one of the top nationally-ranked swimmers of her age group while she was still in high school. With knowing that, one might safely assume that playing a character who calls the ocean their home would be second nature to the actress. In that case, I have the perfect Marvel character for this situation.
The MCU still has yet to introduce Namor the Sub-mariner, who often referred to as the less popular Marvel Comics iteration of Aquaman, despite predating him by a few years. When they do give him his own flick, they should make it a team-up movie featuring his cousin, Namora, who is also gifted with all your basic semiaquatic abilities. Furthermore, I think no one would argue against giving the heroine her own movie instead, especially with Katherine Langford as the lead.