---
schema_version: "secwatch.filing_event.v1"
accession: "0001213900-25-086894"
form_type: "8-K"
ticker: "FISN"
cik: "0001918102"
company_name: "DEEP FISSION, INC."
filed_at: "2025-09-11T23:59:59+00:00"
generated_at: "2026-05-17T06:54:40.659987+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Deep Fission completes reverse merger with Surfside, raises $30M for nuclear reactors

## Summary
- Merger closed Sept 5, 2025; Deep Fission becomes public via reverse merger with Surfside Acquisition.
- Raised $30M ($3/share) in private placement; net ~$26M for R&D, working capital, and pilot reactor.
- New leadership: Elizabeth Muller (CEO), Richard Muller (CTO), William 'Mark' Schmitz (CFO).
- 50.8M shares outstanding post-merger; Legacy Deep Fission holders get 38.5M shares.
- Company developing 15 MWe underground pressurized water nuclear reactors in boreholes one mile deep.

## SEC filing metadata
- accession: 0001213900-25-086894
- form_type: 8-K
- ticker: FISN
- cik: 0001918102
- company_name: DEEP FISSION, INC.
- filed_at: 2025-09-11T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 1.01, 2.01, 3.02, 3.03, 4.01, 5.01, 5.02, 5.03, 5.06, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1918102/000121390025086894/0001213900-25-086894-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1918102/000121390025086894/ea0256443-8k_deep.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001213900-25-086894
- JSON: https://secwatch.observer/filing/0001213900-25-086894.json
- Plain text: https://secwatch.observer/filing/0001213900-25-086894.txt

## Key facts
- Governance Changes
  DEEP FISSION, INC.: Ceased to be a shell company as a result of the merger.
  - Change: shell status
  source text: As a result of the Merger, we have ceased to be a shell company.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1918102/000121390025086894/0001213900-25-086894-index.htm
- Governance Changes
  DEEP FISSION, INC.: Amended and restated bylaws in their entirety at the effective time of a merger.
  - Change: bylaw amendment
  source text: At the Effective Time, we amended and restated our bylaws in their entirety.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1918102/000121390025086894/0001213900-25-086894-index.htm
- Governance Changes
  DEEP FISSION, INC.: Amended and restated certificate of incorporation at the effective time of a merger.
  - Change: charter amendment
  source text: At the Effective Time, we amended and restated our certificate of incorporation.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1918102/000121390025086894/0001213900-25-086894-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.