Declension table of ?samudravastra

Neuter	Singular	Dual	Plural
Nominative	samudravastram	samudravastre	samudravastrāṇi
Vocative	samudravastra	samudravastre	samudravastrāṇi
Accusative	samudravastram	samudravastre	samudravastrāṇi
Instrumental	samudravastreṇa	samudravastrābhyām	samudravastraiḥ
Dative	samudravastrāya	samudravastrābhyām	samudravastrebhyaḥ
Ablative	samudravastrāt	samudravastrābhyām	samudravastrebhyaḥ
Genitive	samudravastrasya	samudravastrayoḥ	samudravastrāṇām
Locative	samudravastre	samudravastrayoḥ	samudravastreṣu

Compound samudravastra -

Adverb -samudravastram -samudravastrāt