Declension table of ?samudravastra

Masculine	Singular	Dual	Plural
Nominative	samudravastraḥ	samudravastrau	samudravastrāḥ
Vocative	samudravastra	samudravastrau	samudravastrāḥ
Accusative	samudravastram	samudravastrau	samudravastrān
Instrumental	samudravastreṇa	samudravastrābhyām	samudravastraiḥ samudravastrebhiḥ
Dative	samudravastrāya	samudravastrābhyām	samudravastrebhyaḥ
Ablative	samudravastrāt	samudravastrābhyām	samudravastrebhyaḥ
Genitive	samudravastrasya	samudravastrayoḥ	samudravastrāṇām
Locative	samudravastre	samudravastrayoḥ	samudravastreṣu

Compound samudravastra -

Adverb -samudravastram -samudravastrāt