They will have the NATO band (230-399 MHz AM) & VHF Air AM. Probably VHF Marine FM too (try :71 & :73).
NATO band will be used to talk to any navy ships.
Try 312.5 which is "Fleet Common Deck" and may be used by multiple ships especially those without their own dedicated frequencies.
It is also used by land-based helipads.
For air to air comms, they are reported to have VHF Low from maybe 30-50 plus odd military bands (FM) inc 72.8-76.7, 78-80, 84-85, 149-149.9, 153.5-154
Remember you are not likely to hear air-to-air much from one heli anyway, there need to be 2 or more nearby.
And there may be Polycon in use which will be UHF FM (Try around 419 MHz)
That's a lot of channels to search so good luck.
I reserve the right to ignore people who have made no attempt to the read the manual, and expect others to do it for them.