Updated.
The swamp wyrm’s favored hunting method is to lie barely submerged in murky water (it can see perfectly through it), then grab anything that comes down to drink. This tactic gives it a +2 bonus to surprise
Shall we borrow this?
*Swamp landwyrms have a +4 racial bonus on Hide checks when in swamp environments. This bonus on Hide checks increases to +8 when the landwyrm is immobile.
Skills: 84
Upthread, Leopold suggested Spot, Listen, Hide, Knowledge (Nature)
I'd recommend replacing Knowledge (nature) with Move Silently.
Feats: 7
Upthread, Leopold suggested Power Attack, Improved Bull Rush, Improved Over Power, Awesome Blow, Combat Reflexes, Alertness, Snatch
I like Awesome Blow, Combat Reflexes, Improved Bull Rush, and Power Attack from that list. I think Improved Overrun (is that what you meant by Over Power?) isn't too beneficial for its typical tactics, and Snatch is a bit redundant with its improved grab ability. Alertness is fine if we can't find something more exciting.
I'd recommend adding to that list Improved Critical (bite) and Weapon Focus (bite), since its combat success hinges almost solely on a successful bite. Improved Initiative seems a good fit, too.