Buy Canon 1DX and 5D Mark III?

The goal is shooting indoor sports, shooting birds in the mangrove forest and other basic tasks such as portraits.

Because often have to work in low-light environments and wet, so I need a moisture-proof body / dust / mist good and less grain at high ISO.

I know that almost surpassed 1DX, but it's too heavy, very expensive, difficult to use for shooting underwater instruments, steadycam ...

I just need to advise the Canon body for itself is wholly owned by Canon's lens only. The lens you are using: 70-200 IS II; 300 f / 2.8 IS; 200 f / 2 IS;200-400mm f / 4L IS USM Extender 1.4x Lens with Internal.

So should I give a large sum to buy 1DX or just 5D Mark III?

Thank you to everyone who gave advice.