As an ex waterbird Instructor (S61) and now current dunker victim, stats then and now show that helos will remain upright up to sea state 1 without floats and SS3 with floats. If SAS is kept in, it will increase the risk of a tip strike with the swell as the tip path plane hunts for the level attitude. Because of the lack of a water anchor the helo will float beam on also increasing the chance of a tip strike.
Unless the a'c is designed to float for prolonged periods (S61 / Sea Sprite etc), you will most certainly sink within seconds without floats. In a calm SS there is a good chance it will sink vertically without toppling, especially if the lower section fills with water quickly. But the sea is never calm!!! So it is almost a certainty that it will (a) roll over inverted and (b) dive nose down after it is fully submerged [For light helos it is estimated that it could sink up to 8'/second....all in the dark, too
If in doubt...do the dunker...Duty of care and all that for the establishment, tremendous confidence for the crew.