In the several 3D E-SCAN surveys that have involved true swamps, a couple have had the advantage of a frozen-surface, winter survey.
Where schedules or access issues do not permit a winter project, or where there is no seasonal "solid freeze" available, swamps must be traversed fully wet. 3D E-SCAN 's principal wiring can be laid on the most convenient route around the worst parts, with single wires pushed into place at adjacent individual electrode sites by whatever means is possible. Missing one or two swamp locations usually doesn't affect overall 3D results, the issue becoming important from a data set integrity standpoint only if three or more sites in close proximity will be missed.
Low topographic areas are always of interest in terms of possible structure or alteration below. However, the loss of surface electrode sites doesn't much affect the mapping of the area directly beneath the swamp, which is sampled primarily by electrodes located well outside of the surface swamp area. A few of the shallowest measurements may be all that's missing. The deeper data gaps resulting from missed swamp-area electrodes will be located some distance out from the edge of the swamp, where data from many other orientations will be fully sampling the volume in question.
An E-SCAN setup is permitted to miss up to 10% of its stations entirely and it will still deliver a fully objective, true 3D result.
In general, occasional swamp areas will be managed in much the same manner as lakes, but without the lake's advantage of easy boating (or wading) and unobstructed helicopter access.
A project consisting principally of swamps will be closely examined for an optimum, locally-customized survey approach that may involve specialized equipment.
Time, cost, risk?