When he got to the beach the seal's head popped up fifty yards from the landing. He rose until his shoulders were out of water and made frisky motions with his head, telling Clint to come on in. Then he dived, to reappear in the shallow water almost at Clint's feet. He came out, frisking and beaming good will; Clint couldn't even scold him for having made so much trouble.
上の引用文の "frisky"、"frisking" は何でしょう? まず "frisk" で調べます。
・Compact Oxford English Dictionary:
1 [with object] (of a police officer or other official) pass the hands over (someone) in a search for hidden weapons, drugs, or other items
2 [no object, with adverbial of direction] skip or leap playfully; frolic: spaniels frisked around me
・Wordnik:
1.To move about briskly and playfully; frolic.
2.To search (a person) for something concealed, especially a weapon, by passing the hands quickly over clothes or through pockets.
飛行場でたまに身体を触られての所持品検査を受けることがありますがその時の "frisk" とは違って引用文の "frisking" は楽しい方の意味ですね。 "frisky" は "frisk" の形容詞形だと思いますが一応意味を辞書で確認しておきます。
・Compact Oxford English Dictionary: playful and full of energy: he bounds about like a frisky pup
・Wordnik: Energetic, lively, and playful: a frisky kitten.
動物や人間の子供の動作表現に使われる事が多いのでしょうね。