1. Get the Training, I think all the other comments have keyed you onto this
2. Skip those stupid SMACO things, it will take you over an HOUR of pumping to make enough air for a 2 minute dive, does that sound fun/efficient?
3. Get this, https://www.amazon.com/dp/B000T5U2YK/?coliid=I1PXH7E6VKJZOY&colid=1VNX8QSC2S8F4&psc=1&ref_=lv_ov_lig_dp_it and the small tank. Then get a transfer whip and an AL80, you can refill the little tank multiple times and at only 8' you won't use that much air. You don't need a full sized BC for what you want to do.

or download a freediving app on your phone, practice a few times at night and within a month you'll be able to hold your breath for 3+ minutes.