The swim isn't the only scenario...
1. Missile attack then air drop
2. Hide troops in regularly scheduled flights
3. Missile attack until surrender
4. Internal Taiwanese coup (helped by China)
5. Missile attack, followed by simultaneous beach landing and airdrop
I'm not saying any of these would be successful, but there are several scenarios to look at. Very interesting scenarios I might add.
The big question is whether the US will intervene with its navy.
One non-military response would be to cancel all Chinese held US treasury bonds/bills. That would HURT.
Missile attacks are useless without nukes. About all the atatcker accomplishes is to alert the defender.
Hiding troops in regularly scheduled flights is pretty stupid--because it would be rather obvious (a bunch of young men suddenly start showing from Mainland China--yup, nobody gets suspicious...)
Beach landings are out of the question unless Louis Farrakhan is setting up the Million Man Swim.