We investigate the assimilation of data that are collected while Lagrangian ocean instruments are in transit between surfacings. Effectively utilizing such data presents a challenge as the subsurface paths of these instruments are unknown. We introduce an observation operator that takes these data into account in addition to the data that are typically assimilated. A key point is that the subsurface, en-route paths of these ocean instruments are estimated as part of the assimilation scheme. We will also discuss a hybrid assimilation scheme being developed that is quite well suited to Lagrangian data assimilation. Finally we will posit how we see these two schemes being used together.