otter warns me off

[stevio]

On the bank of a small lake i disturbed an otter who rushed into the dark under some bushes it seemed to bob its head up and down and thump what i presume was its tail on the ground before disapearing into the dark it probably did nt know what i was at first there are lots of other animals about ie. dogs fox polecats mink stoat ect.
is this usual behavior?

[bobbarber]

Could be a danger warning, as in rabbits with a foot thump or a beaver with a tail smack on the water, don`t know if it`s normal behaviour in otters...Bob