Hey I have the same issue as you with my SUV - I use something that is idential to this works great. I lock my keys to the front grill of the vehicle - its far enough away that the proximity sensor won't unlock the car.
That one I linked includes a little proximity blocker as well - I haven't tried it so I can't vouch for it.
there are key locks where you can lock on your car. something like this: https://www.amazon.com/FCS-KeyLock-Safe-Secure-Combination/dp/B07X5ZZ4JW
and for your phone, either a waterproof case you can wear around your neck or a sports case you can wear around your arm. if your phone is not waterproof you can put is in a ziplockbag an put it in the case. https://www.amazon.com/-/de/dp/B07JL74R2J/ref=mp_s_a_1_1?dchild=1&keywords=sport+phone+cases&qid=1600408487&sprefix=sport+phone+&sr=8-1
if you wear a lifejacket you can put your phone in the lifejacket.