In August 1993, prior to the end of apartheid, the Multiparty Negotiating Forum in South Africa passed a resolution calling for "the incorporation-reintegration of Walvis Bay and the Off-Shore Islands into Namibia." The Transfer of Walvis Bay to Namibia Act was passed by the Parliament of South Africa that year. Following the signing of a treaty between the two countries, South Africa formally transferred sovereignty of Walvis Bay and the Penguin Islands to Namibia on 1 March 1994.

Based on this passage, when did walvis bay become part of namibia? Let's think fast. Stream of consciousness:
To answer this question, we should know that: Following the signing of a treaty between the two countries, South Africa formally transferred sovereignty of Walvis Bay and the Penguin Islands to Namibia on 1 March 1994. So the final answer is 1 March 1994.