Note 6 - Stockholders' Equity and Dilutive Equity Instruments - Dilutive Equity Instruments (Details) - shares	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Common stock, shares outstanding (in shares)	50,780,847	50,554,179	41,716,885
Total (in shares)	52,607,361		44,348,132
Restricted Stock Units and Stock Options [Member]
Common stock shares reserved (in shares)	1,637,393		1,736,037
New Creditor Warrants [Member]
Common stock shares reserved (in shares)	81,244		465,398
GulfMark Creditor Warrants [Member]
Common stock shares reserved (in shares)	107,877		429,812