Poseidon's rhymes with:
haydn's, widens, abandons, arden's, baden's, borden's, brandon's, breeden's, broadens, burdens, camden's, chernomyrdin's, cherumirdan's, coloradans, darden's, edens, garden's, gardens, giddens, golden's, gooden's, gordon's, harden's, hardens, haydn's, holden's, jordan's, jordans, landon's, linden's, london's, maidens, mcfadden's, meldons, nevadans, ogden's, pardons, riordan's, rwandan's, rwandans, saddens, siddens, siddons, sweden's, tendons, warden's, wardens, wardens', weldon's, widens
Poseidon's sounds like:
pakistan's, pakistanis, pastimes, pasting, picketing, pistons, pocketing, positioning, positions, postdating, posthumous, posting, postings, pseudomonas, pseudonyms, psychodynamic