Phugoid down to the ocean surface ?
We must remember that the 777 is a Fly By Wire aircraft - even with the Autopilot off. There is also a ram-air turbine after the batteries fail - which they wouldn't in a descent from 35K or so (Boeing had to consider a dual engine failure - volcanic ash, fuel starvation, and such ).
The Fly By Wire computer would maintain a speed above stall speed for whatever the configuration was and a fairly constant descent rate of maybe 800-1200 feet per minute - even hands off! Also, the bank angle could be anything - maybe even level. Therefore a rough ditching (somewhat nose up, wings somewhat level) attitude is even possible.
There are many possibilities still - including something like the Helios slow decompression flight with the later turns being accomplished by someone other than the flight crew - or any kind of "deliberate action".