Yes, since Bestial Form does not require concentration
On pages 9 and 10 of the UA article, combinations of disciplines when spending psi points is covered.
Using a Discipline
Each psionic discipline has several ways you can use it, all contained
in its description. The discipline specifies the type of action and
number of psi points it requires. It also details whether you must
concentrate on its effects...{snipped for brevity}
How do we know if we need to concentrate?
Concentration
Some options require concentration to maintain their effects. This
requirement is noted with “conc.” after the option’s psi point cost.
The “conc.” notation is followed by the maximum duration of the
concentration. For example, if an option says “conc., 1 min.,” you can
concentrate on its effect for up to 1 minute.
Bestial Form does not have the notation of "conc. {x time}" on page 11.
Can we combine two options from one feature? Yes.
Combining Psionic Effects
The effects of different psionic disciplines add together while the
durations of the disciplines overlap. Likewise, different options from
a psionic discipline combine if they are active at the same time.
However, a specific option from a psionic discipline doesn’t combine
with itself if the option is used multiple times.
As long as you use two different options, you aren't "combining it with itself." In your example, you can combine the amphibious with the swimming and spend 2 points for each, and have them both active at once with the first expiring just a little before the second. (Let's say 6 seconds, to align with the action economy).