When I was first exploring Methode Naturelle and “natural” movement training one of my favorite trainings was to go down to whatcom falls park to my favorite pool in the creek, dive in, swim down, pick up a big rock and carry it along the bottom of the pool against the current, this was extremely challenging but felt totally safe. I would then let go kick off and shoot down with the current to an overhanging log, muscle up, balance across, then walk back to the start dive in and repeat.
The underwater carry is a great example of mixing different movement modalities, swimming or aquatic movement, walking, balance, carrying, breath holding IE apnea. Compared to the average gym drill this is development on far more levels. Our capacity as human beings is not just how big our muscles are, how much weight we can move or how much power output we can generate on simple exercises its about skillful movement and the ability to tolerate high numbers of chaotic variables, like the slick rocks on the bottom of pool the current and its eddies, and doing it all while having to hold your breathe.
After these training sessions I often had the greatest sense of peace, and would sit in the sun and meditate.
My challenge for you is if you are decent swimmer and have safe place to play work on weighted movement underwater.
Here is good example of some basic drills.