I think they are hiring as everyone who can is leaving either to emirates or etihad, even qatar. Omanair is hugely disorganized and you spend your 7 days off/month chasing somebody in the office to do their job or in banks, getting stamps, certificates etc.
Oman itself is boring as hell - forget about public pools or aquaparks, parks or cycling trails. you can go for a walk in one of the two shopping malls
never heard about apartment on water (what water?! sea? are you friends trying to impress maybe?) housing allowance been up from 350 to 600 for F/O which can get you a decent house in cheap areas such as Al Mawaleh or Al Hail.
pay? less than the others in the gulf but you will probably save a bit more as there is nothing to do and nothing to spend money on (unless you have 4 kids and pay for their schooling and after school activities)